It's pretty simple! Basically, sketch out your image, and whatever you want to NOT be black, you just paint over with gouache. Once you cover it in india ink and wash it, the gouache dissolves and leaves only the paper, giving it a bit of a cut out feel. Then you can go nuts with colour however you want!

I'm out of gouache, but maybe I can make something with that technique at some point for Steemit this year...