Danish Building Blocks

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/bZ649dUCkTy

I want to make a mold in the style of a certain Danish building block we all know and love. Had I gone looking I probably could have found what I wanted already made, but I also wanted to improve my skills with TinkerCAD. Since these will be the basis for a mold, they're solid, and will not fit together.