how to package a java application with flatpak?

recently I've started working with an open source java gui app that uses jpackage to generate system packages for distributions.

I'm interested in creating a flatpak for this, but I'm not sure what best practices look like for this. Should I attempt to take the files that are generated by jpackage and put those into a flatpak, or should I just take the jar file alone as provide that with a dependency on a runtime that provides java?

fair warning I am a noob in regards to flatpak