Look at this. I got tired of picking up all the boxes on top of the one I wanted so I made a rack. And painted it black. It is cool. It holds 12 boxes.
The sides are 1/2 plywood. The shelves are 1/2 wide stips of plywood. They are 3/16 thick and glued into small slots in the ply wood. Each slot is 2.5 inches high, about 14 wide. The hole thing is 30 wide and 15 high.