I wanted to start with something simple. So I tried making just some boxes that have the same dimensions as the Infinite Crypt Elements. The library sells material that I could cut (Melamine Lined MDF). The width of these boards was 3/16", whereas all the Infinite Crypt elements was using 1/8" wide material.
Since that's all I had on hand, I created my elements with the 3/16" thick material. The first elements came out pretty well.
I was happy with these, and they fit in perfectly with the other elements I had purchased. So I decided to keep going and make more complicated things.