This is a tray that stacks.
I cut it on a 30w Epilog Zing out of 3mm MDF.
Long story short... I've been using Legos to teach for about 11 years and during this time I've spent (or rather my school has spent) probably $50k on Lego kits. As you can imagine, this is a whole lot of Legos. If you have one kid with Legos, you know what sort of mess can be made. Multiply that by hundreds of kids and many, many times more Legos. I looked around for all sorts of inexpensive (because I spent all my money on Legos) sorting options. I found a few that looked like they might fit the bill but I couldn't figure out how to get them cut correctly so I made my own.
I modified the layout to try to minimize waste. The "improved" version fits on a 6" x 9.5" piece of MDF.
I laser cut this on a 30w Epilog Zing engraver out of 3mm MDF that you can get at any home center for less than $10 for a 4'x8' sheet.
This should cut entirely in vector (no raster). I set my speed to 30%, power to 100% and frequency to 600hz and it seemed to come out correctly.
Since the bed on my laser is only about 11" by 16", I wanted all parts to be cut out of a piece that was roughly the size of sheet of paper. The base is 4.5" long and 3" wide. Height is about little more than 2.25" with the sides angled out by about 4 degrees. Assemble the front, back, and sides first and then pop it onto the bottom plate. Tabs on the top of the sides will lock into widened second and fifth holes on the bottom if you stick another tray on top so stack to your heart's content.
I didn't put any glue on this but it might not be a bad idea to put some plain white glue or wood glue on the joints to keep it together.