In a project recently I needed to use the filesystem features that you get in Laravel, but in the Lumen framework instead. I couldn't find a clear tutorial online to tell you have to do this, however after some research got it working using the following instructions.

First, we need to include some packages using composer; in my case I was going to be using Amazon S3 storage, so I included that. 

composer require league/flysystem

After installing the league/flysystem package, you'll see a list of additional packages which it recommends you install for things such as Amazon S3, FTP etc. Install the additional packages that you think you'll use. I installed Amazon S3;

composer require league/flysystem-aws-s3-v3

Next we need to grab the configuration file from Laravel, copy the file /config/filesystems.php from Laravel and place the file into the /config folder of your Lumen project. You'll want to edit the file to provide any details required for your chosen storage, for me I amended the configuration file to pull in values from the environment file;

'disks' => [ 
 's3' => [  
   'driver' => 's3',  
   'key' => env('S3_KEY'),  
   'secret' => env('S3_SECRET'),  
   'region' => env('S3_REGION'),  
   'bucket' => env('S3_BUCKET'),  
 ], 
],

In my env file I added the credentials for my Amazon S3 account.

S3_KEY=your_s3_key
S3_SECRET=your_s3_secret
S3_REGION=eu-west-1
S3_BUCKET=the_name_of_your_bucket

Edit your /bootstrap/app.php file and uncomment the following line;

$app->withFacades();

In the same file, uncomment;

$app->register(App\Providers\AppServiceProvider::class);

Finally, edit the file /providers/AppServiceProvider.php and add the following;

$this->app->singleton('filesystem', function ($app) {  
    return $app->loadComponent('filesystems', 'Illuminate\Filesystem\FilesystemServiceProvider', 'filesystem'); 
    });

Hopefully you should now be able to use the filesystem features in your project as you would in a Laravel project.