This is a fine approach too. Just be aware that most modern mcu would be a hell to mount on DIY. Also, this works on literally any paper with super bold print setting.

I would recommend trying copper-based etch, it’s easier to work that FeCl3 (it’s transparent, to begin with, and not as corrosive to other stuff)

Also, I’ve heard some dudes made really nice stencils for paste with some cheap hobby blade CNC tools on cardboard, there are models that have orders of mad higher precision than advertized. Never tried this myself though, lazer cut stainless steel plates from factory are just soooo good (and also a source of high quality steel in a workshop when you don’t need them anymore, they make perfect wood scrapers and such)