There are lots of online tutorials for how to make Tetris shelves. Most of the ones we found were a little more time-consuming complicated than what we wanted to do (we like to keep things pretty simple around here). By all means, if you plan to sell yours or gift them, you probably want to miter, dovetail, bevel, etc., but yeah . . . we skipped all that. Plus, we don't really have the necessary equipment for that kind of work.
For ours, we started with some 1/2-inch plywood that we had in the garage. A sheet of it is just over 10 bucks at Home Depot. We drew a grid on it, to be able to easily draw our Tetris shapes out. You know the ones. Making a grid like this means you don't have to measure your individual cuts (just count out the squares). Our grid squares were each 4 inches by 4 inches.
