Yeah, I've created my first (dummy) #GNU #Guix package! I've also set up a custom channel for the package (and the OpenPGP signing scheme).

https://guix.gnu.org/manual/en/html_node/Channels.html

It took me a few attempts to get things right (e.g. my Guile module path was wrong), but I can finally Guix-install my custom hello-world app.

Hope I'll be able to make good use of this in the future, e.g. to help with packaging.