form.blade.php

@section('content')
    <div class="card">
        <div class="card-body">
            @if ($errors->any())
                <div class="alert alert-danger">
                    <ul>
                        @foreach ($errors->all() as $error)
                            <li>{{ $error }}</li>
                        @endforeach
                    </ul>
                </div>
            @endif
            
            {{ Form::model($course, ['url' => route('upload_s3'), 'files' => true]) }}
              <div class="form-group">
                {{ Form::label('Imagen', null, ['class' => 'control-label']) }}
                {{ Form::file('upload') }}
              </div>
            
              <div class="form-group btn.purple">
                {{ Form::submit('Subir archivo') }}
              </div>

            {{ Form::close() }}
        </div>
    </div>
@stop

routes.php

<?php 
use Illuminate\Support\Facades\Route;
use Illuminate\Support\Facades\Storage;

Route::post('upload', function () {
   $file = request()->file('upload');
   $upload = Storage::disk('s3')->put('courses/' . $file->getClientOriginalName(), $file, 'public');
})->name('upload_s3');