With no idea of the size I started to roughly layout the idea in EAGLE but soon noticed that I'd run into the size restriction of the "free" version I have. So I thought to myself, why not use KiCad for this idea and it worked out! Overcoming some UI quirks and stuff I'm not used to is a small price to pay for an unlimited boardsize, I thought to myself.
But I soon missed the auto-router :( I've routed everything and finally got to the point where I was ready for an OSHPark upload... but wow that price! - a pretty fair price and I probably can get it cheaper from a pcb producer you'd no doubt want to write in the comments, but I've decided to try a good old perfboard instead.
So here is what I've produced in Inkscape so far, it really helped to draw the 15 x 20 cm2 and notice that I've bought all the wrong sizes, starting with a 10x22 board and a 12x18 board. I plan on adding a decal before soldering, maybe a gold sticker and print something purple on it as a tribute to the OSHPark boards I've never ordered.