Small Shelf - Flat

I really loved the small shelf by RileyDesigns, however I didn't like it didn't have a bottom shelf, and I wanted to make sure if I put things on it and then slid the shelf side to side, all of my stuff would move with it. So I popped it into a CAD program to add the bottom shelf, but that's when I realized the two existing shelves were not actually 100% flat. This wasn't going to work for me because I wanted to put some delicate glass items on it, so I swapped out all the shelves but left the b