I did this project quite a while ago and sharing just for the fun and the absurdity.
I actually cut the layers shortly after getting my GF and then waited more than a year to glue it up.
I had originally planned to put a thin piece of clear acrylic with tick marks for # of various coins in the openings, but never tried it.
The openings are just wide enough so that I could interlock the pieces in the layout and waste less material.