'providers' => [
    //...
    NilPortugues\Laravel5\JsonApi\Laravel5JsonApiServiceProvider::class,
],

<?php
Route::group(['namespace' => 'Api'], function() {
    Route::resource('employees', 'EmployeesController');    
    Route::get(
        'employees/{employee_id}/orders', [
        'as' => 'employees.orders',
        'uses' => 'EmployeesController@getOrdersByEmployee'
    ]);
});
//...

<?php namespace App\Model\Database;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Foundation\Validation\ValidatesRequests;

class Employees extends Model
{
    public $timestamps = false;
    protected $table = 'employees';    
    protected $primaryKey = 'id';
    protected $appends = ['full_name'];

    /**
     * @return \Illuminate\Database\Eloquent\Relations\HasOne
     */
    public function latestOrders()
    {
        return $this->hasMany(Orders::class, 'employee_id')->limit(10);
    }

    /**
     * @return string
     */
    public function getFullNameAttribute()
    {
        return $this->first_name.' '.$this->last_name;
    }
}

<?php namespace App\Model\Database;

use Illuminate\Database\Eloquent\Model;

class Orders extends Model
{   
    public $timestamps = false;
    protected $table = 'orders';
    protected $primaryKey = 'id';

    /**
     * @return \Illuminate\Database\Eloquent\Relations\HasOne
     */
    public function employee()
    {
        return $this->belongsTo(Employees::class, 'employee_id');
    }
}

<?php namespace App\Model\Api;

use App\Model\Database\Employees;
use NilPortugues\Api\Mappings\JsonApiMapping;

class EmployeesTransformer implements JsonApiMapping
{
    /**
     * Returns a string with the full class name, including namespace.
     *
     * @return string
     */
    public function getClass()
    {
        return Employees::class;
    }

    /**
     * Returns a string representing the resource name 
     * as it will be shown after the mapping.
     *
     * @return string
     */
    public function getAlias()
    {
        return 'employee';
    }

    /**
     * Returns an array of properties that will be renamed.
     * Key is current property from the class. 
     * Value is the property's alias name.
     *
     * @return array
     */
    public function getAliasedProperties()
    {
        return [
            'last_name' => 'surname',
            
        ];
    }

    /**
     * List of properties in the class that will be  ignored by the mapping.
     *
     * @return array
     */
    public function getHideProperties()
    {
        return [
            'attachments'
        ];
    }

    /**
     * Returns an array of properties that are used as an ID value.
     *
     * @return array
     */
    public function getIdProperties()
    {
        return ['id'];
    }

    /**
     * Returns a list of URLs. This urls must have placeholders 
     * to be replaced with the getIdProperties() values.
     *
     * @return array
     */
    public function getUrls()
    {
        return [
            'self' => ['name' => 'employees.show', 'as_id' => 'id'],
            'employees' => ['name' => 'employees.index'],
            'employee_orders' => ['name' => 'employees.orders', 'as_id' => 'id']
        ];
    }

    /**
     * Returns an array containing the relationship mappings as an array.
     * Key for each relationship defined must match a property of the mapped class.
     *
     * @return array
     */
    public function getRelationships()
    {
        return [];
    }
} 

<?php namespace App\Model\Api;

use App\Orders;
use NilPortugues\Api\Mappings\JsonApiMapping;

class OrdersTransformer implements JsonApiMapping
{
    /**
     * {@inheritDoc}
     */
    public function getClass()
    {
        return Orders::class;
    }
    /**
     * {@inheritDoc}
     */
    public function getAlias()
    {
        return 'order';
    }
    /**
     * {@inheritDoc}
     */
    public function getAliasedProperties()
    {
        return [];
    }
    /**
     * {@inheritDoc}
     */
    public function getHideProperties()
    {
        return [];
    }
    /**
     * {@inheritDoc}
     */
    public function getIdProperties()
    {
        return ['id'];
    }
    /**
     * {@inheritDoc}
     */
    public function getUrls()
    {
        return [
            'self'     => ['name' => 'orders.show', 'as_id' => 'id'],
            'employee' => ['name' => 'employees.get', 'as_id' => 'employee_id'],
        ];
    }
    /**
     * {@inheritDoc}
     */
    public function getRelationships()
    {
        return [];
    }
} 

<?php
use App\Model\Api\EmployeesTransformer;
use App\Model\Api\OrdersTransformer;

return [
    EmployeesTransformer::class,
    OrdersTransformer::class,
];

$app->register(\NilPortugues\Laravel5\JsonApi\Laravel5JsonApiServiceProvider::class);
$app->configure('jsonapi');

$app->withFacades();

<?php
$app->group(
    ['namespace' => 'Api'], function($app) {
        $app->get(
            'employees', [
            'as' => 'employees.index',
            'uses' =>'EmployeesController@index'
        ]);
        $app->post(
            'employees', [
            'as' => 'employees.store',
            'uses' =>'EmployeesController@store'
        ]);
        $app->get(
            'employees/{employee_id}', [
            'as' => 'employees.show', 
            'uses' =>'EmployeesController@show'
        ]);
        $app->put(
            'employees/{employee_id}', [
            'as' => 'employees.update', 
            'uses' =>'EmployeesController@update'
        ]);
        $app->patch(
            'employees/{employee_id}', [
            'as' => 'employees.patch',
            'uses' =>'EmployeesController@update'
        ]);
        $app->delete(
            'employees/{employee_id}', [
            'as' => 'employees.destroy',
            'uses' =>'EmployeesController@destroy'
        ]);
        
        $app->get(
            'employees/{employee_id}/orders', [
            'as' => 'employees.orders', 
            'uses' => 'EmployeesController@getOrdersByEmployee'
        ]);
    }
);
//...

<?php namespace App\Http\Controllers;

use App\Model\Database\Employees;
use NilPortugues\Laravel5\JsonApi\Controller\JsonApiController;

class EmployeesController extends JsonApiController
{
    /**
     * Return the Eloquent model that will be used 
     * to model the JSON API resources. 
     *
     * @return \Illuminate\Database\Eloquent\Model
     */
    public function getDataModel()
    {
        return new Employees();
    }
}

//Constructor and defined actions
public function __construct(JsonApiSerializer $serializer);
public function listAction();
public function getAction(Request $request);
public function postAction(Request $request);
public function patchAction(Request $request);
public function putAction(Request $request);
public function deleteAction(Request $request);

//Methods returning callables that access the persistence layer
protected function totalAmountResourceCallable();
protected function listResourceCallable();
protected function findResourceCallable(Request $request);
protected function createResourceCallable();
protected function updateResourceCallable();

//Allows modification of the response object
protected function addHeaders(Response $response);

<?php namespace App\Http\Controllers;

use App\Model\Database\Employees;
use App\Model\Database\Orders;
use NilPortugues\Laravel5\JsonApi\Controller\JsonApiController;

class EmployeesController extends JsonApiController
{
    /**
     * Return the Eloquent model that will be used 
     * to model the JSON API resources. 
     *
     * @return \Illuminate\Database\Eloquent\Model
     */
    public function getDataModel()
    {
        return new Employees();
    }    
    
    /**
     * @param Request $request
     *
     * @return \Symfony\Component\HttpFoundation\Response
     */
    public function getOrdersByEmployee(Request $request)
    {       
        $apiRequest = RequestFactory::create();
        $page = $apiRequest->getPage();

        if (!$page->size()) {
            $page->setSize(10); //Default elements per page
        }

        $resource = new ListResource(
            $this->serializer,
            $page,
            $apiRequest->getFields(),
            $apiRequest->getSort(),
            $apiRequest->getIncludedRelationships(),
            $apiRequest->getFilters()
        );
        
        $totalAmount = function() use ($request) {
            $id = (new Orders())->getKeyName();
            return Orders::query()
                ->where('employee_id', '=', $request->employee_id)
                ->get([$id])
                ->count();
        };

        $results = function()  use ($request) {
            return EloquentHelper::paginate(
                $this->serializer,
                Orders::query()
                    ->where('employee_id', '=', $request->employee_id)
            )->get();
        };

        $uri = route('employees.orders', ['employee_id' => $request->employee_id]);
        
        return $resource->get($totalAmount, $results, $uri, Orders::class);
    }
}

<?php namespace App\Http\Controllers;

use App\Model\Database\Employees;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Support\Facades\DB;
use NilPortugues\Api\JsonApi\Server\Errors\Error;
use NilPortugues\Api\JsonApi\Server\Errors\ErrorBag;
use NilPortugues\Laravel5\JsonApi\Controller\JsonApiController;

class EmployeesController extends JsonApiController
{
    /**
     * Now you can actually create Employee and Orders at once.
     * Use transactions - DB::beginTransaction() for data integrity!
     *
     * @return callable
     */
    protected function createResourceCallable()
    {
        $createOrderResource = function (Model $model, array $data) {
            if (!empty($data['relationships']['order']['data'])) {
                $orderData = $data['relationships']['order']['data'];

                if (!empty($orderData['type'])) {
                    $orderData = [$orderData];
                }

                foreach ($orderData as $order) {
                    $attributes = array_merge($order['attributes'], ['employee_id' => $model->getKey()]);
                    Orders::create($attributes);
                }
            }
        };

        return function (array $data, array $values, ErrorBag $errorBag) use ($createOrderResource) {

            $attributes = [];
            foreach ($values as $name => $value) {
                $attributes[$name] = $value;
            }

            if (!empty($data['id'])) {
                $attributes[$this->getDataModel()->getKeyName()] = $values['id'];
            }

            DB::beginTransaction();
            try {
                $model = $this->getDataModel()->create($attributes);
                $createOrderResource($model, $data);
                DB::commit();
                return $model;
                
            } catch(\Exception $e) {
                DB::rollback();
                $errorBag[] = new Error('creation_error', 'Resource could not be created');
                throw $e;
            }
        };
    }

}

<?php namespace App\Model\Database;

use Illuminate\Database\Eloquent\Model;
use Illuminate\Foundation\Validation\ValidatesRequests;

class Employees extends Model
{
    public $timestamps = false;
    protected $table = 'employees';    
    protected $primaryKey = 'id';
    protected $appends = ['full_name'];
    
    /**
     * @var array
     */
    protected $fillable = [
        'company',
        'last_name',
        'first_name',
        'email_address',
        'job_title',
        'business_phone',
        'home_phone',
        'mobile_phone',
        'fax_number',
        'address',
        'city',
        'state_province',
        'zip_postal_code',
        'country_region',
        'web_page',
        'notes',
        'attachments',
    ];

    /**
     * @return \Illuminate\Database\Eloquent\Relations\HasOne
     */
    public function latestOrders()
    {
        return $this->hasMany(Orders::class, 'employee_id')->limit(10);
    }

    /**
     * @return string
     */
    public function getFullNameAttribute()
    {
        return $this->first_name.' '.$this->last_name;
    }
}

<?php namespace App\Model\Database;

use Illuminate\Database\Eloquent\Model;

class Orders extends Model
{   
    public $timestamps = false;
    protected $table = 'orders';
    protected $primaryKey = 'id';
    
    /**
     * @var array
     */
    protected $fillable = [
        'employee_id',
        'customer_id',
        'order_date',
        'shipped_date',
        'shipper_id',
        'ship_name',
        'ship_address',
        'ship_city',
        'ship_state_province',
        'ship_zip_postal_code',
        'ship_country_region',
        'shipping_fee',
        'taxes',
        'payment_type',
        'paid_date',
        'notes',
        'tax_rate',
        'tax_status_id',
        'status_id',
    ];
    
    /**
     * @return \Illuminate\Database\Eloquent\Relations\HasOne
     */
    public function employee()
    {
        return $this->belongsTo(Employees::class, 'employee_id');
    }
}

<?php namespace App\Http\Controllers;

use App\Model\Database\Employees;
use NilPortugues\Laravel5\JsonApi\Controller\JsonApiController;
use Symfony\Component\HttpFoundation\Response;

class EmployeesController extends JsonApiController
{
    //All your supported methods...
    
    /**
     * @param Response $response
     *
     * @return \Symfony\Component\HttpFoundation\Response
     */
    protected function addHeaders(Response $response) {
        $response->headers->set('X-API-Version', '1.0');
        $response->setPublic();
        $response->setMaxAge(60);
        $response->setSharedMaxAge(60);

        return $response;
    }
}