File structure

The only structure you are required to comply is a assets folder with two sub folders: audio and images.

An example:

Flame.audio.play('explosion.mp3');

Flame.images.load('player.png');
Flame.images.load('enemy.png');

The file structure would have to be:

.
└── assets
    ├── audio
    │   └── explosion.mp3
    └── images
        ├── enemy.png
        └── player.png

Don't forget to add these files to your pubspec.yaml file:

flutter:
  assets:
    - assets/audio/explosion.mp3
    - assets/images/player.png
    - assets/images/enemy.png