I wrote sailfish-patch exactly to make developing patches easier also for less technical people. All my patches are built using this tool.
@Seven.of.nine Maybe give it a try? It handles downloading sources and generating packages, and it’s much easier than doing everything by hand.
(@Fellfrosch was planning to write a very easy to follow how-to but for that I first have to fix a hiccup. I didn’t have time yet to give my patches the love they deserve. I’m traveling but when I’m back I’ll look into it again.)