S3 version 2 compatible storage driver for Laravel 5.1+

S3v2ServiceProvider.php

<?php

/**
 * @file
 * Usage:
 *   1. remove the V3 AWS PHP sdk when present
 *     composer remove "league/flysystem-aws-s3-v3"
 *   2. install the V3 AWS PHP sdk when present
 *     composer require "league/flysystem-aws-s3-v2"
 *   3. Add the provider to your config/app.php:
 *     'providers' => [
 *         // Other Service Providers
 *         App\Providers\S3v2ServiceProvider::class,
 *     ],
 *   4. Add your S3 credentials to config/filesystems.php:
 *       'disks' => [
 *           'remote' => [
 *               'driver' => 's3v2',
 *               'key' => 'ACCESS_KEY',
 *               'secret' => 'SECRET_KEY',
 *               'bucket' => 'BUCKET_NAME',
 *               'base_url' => 'BASE_URL'
 *           ],
 *       ],
 */

namespace App\Providers;

use Aws\S3\S3Client;
use Illuminate\Support\Facades\Storage;
use Illuminate\Support\ServiceProvider;
use League\Flysystem\AwsS3v2\AwsS3Adapter;
use League\Flysystem\Filesystem;

class S3v2ServiceProvider extends ServiceProvider
{
    /**
     * Bootstrap the application services.
     *
     * @return void
     */
    public function boot()
    {
        Storage::extend('s3v2', function ($app, $config) {

            $client = S3Client::factory([
                'key'    => $config['key'],
                'secret' => $config['secret'],
                'base_url' => $config['base_url']
            ]);
            return new Filesystem(new AwsS3Adapter($client, $config['bucket']));
        });
    }

    /**
     * Register the application services.
     *
     * @return void
     */
    public function register()
    {
        //
    }
}

Point 2. in the comment you added still has V3 in in it :)