The snapcraft desktop helpers project contains a number of tools to help you create snaps for desktop applications. For example, several environment variables and compatibility symlinks are setup in the desktop-launch wrapper to help ensure the snap can find needed files.
Go to the documentation on snapping graphical applications and follow the instructions for the GUI toolkit that your application uses.
ℹ️ We are currently in the process of moving most of the functionality of the desktop helpers to Snapcraft Extensions. The extensions are much easier to use and contain many improvements, so it's advised to use an extension if one is available for the GUI toolkit that you use.
Please feel free to ask questions in the forum or on Rocketchat if you are having trouble.