Start small
1 Starting with a 2×10" blank, cut to size the box front, back, and sides (A, B). Label the parts to maintain a continuous grain match. From scrapwood, cut a couple extra blanks to the same width and thickness for setting up your box-joint jig.
2 Make a simple box-joint jig for your router table’s miter gauge [Skill Builder]. After dialing in your setup, cut the slots in the front and back (A) [Drawing 1]. Then cut the mating slots in the sides (B).