Packaging a statically linked binary without an SDK?

Hey everyone, I wrote an app I’d like to package as a flatpak.

I’ve read through some docs but they all want me to use an SDK and a runtime.
However, during development, I already made sure this is not necessary, and I have a single, statically linked binary as a result.

I can however not find a way to specify runtime/SDK: none. But all my app needs is to be somewhere and have a few folders bind mounted. The latter of which I was able to find documentation for and should be pretty easy.

I have seen the docs about single file bundles, but apparently these don’t allow updates, which is the main thing I’m looking. That and sandboxing.