Tools and supplies I used:

Table saw (only attempt this project if you’ve been trained on this)
Orbital sander
Drill with 3/32” pilot bit
1 sheet ½” plywood, cut into 4 2’x4’ boards
2’ x 4’ piece of MDF, 1/8” thick
64 #6 flat head phillips wood screws 1-½” long

I made it at Techshop: http://techshop.ws

Step 1: Cutting the Plywood Pieces

Using the table saw, I cut the following lengths from the 2’x4’ pieces:
• 2 pieces that were 31” long (and 2’ wide)
• 1 piece that was 20-11/16” long (and 2’ wide)
• 2 pieces that were 15.5” long (and 2’ wide)
• 1 pieces that were 10-5/16” long (and 2’ wide)
• 12 pieces that were 6” x 11-15/16”
• 7 pieces that were 6-3/8” x 11-15/16”

Step 2: Cutting the Grooves

I then lowered the blade so that only 3/16” was above the table and took off the guard (only do this if you’ve been trained how to, otherwise get help) and cut the following grooves in each of the two 31” pieces (using multiple passes, moving the fence 1/16” each time):

2 grooves that were a tiny bit more than 15/32” wide (so that a piece of plywood wood fit snugly) located 1/3 of the way and 2/3 of the way on the length and cutting across the width (i.e. the grooves were centered at ~10-5/16” and ~20-11/16 and were each 2’ long).

3 grooves that were a tiny bit more than 1/8” wide (so that a piece of 1/8” MDF could fit loosely and be able to slide easily) located so as to split each of the 1/3 compartments that would be made by the previous grooves in half (i.e. these groves should be centered at ~5-1/4”, 15-1/2”, and 25-3/4” and were each 2’ long).

I cut similar grooves in some of the other pieces as follows:

In the 20-11/16” piece I cut a 15/32”+ groove in the midpoint and a 1/8”+ groove in the mid-point of each of the resulting halves (i.e. these 3 grooves will eventually make 4 compartments).

In the two 15.5” pieces I cut a 15/32”+ groove in the midpoint.

In the 10-5/16” piece I cut a 1/8” groove in the midpoint.

I then raised the blade and put the guard back on (only do this if you’ve been trained how to, otherwise get help). I then cut each of the grooved pieces in half lengthwise (to make 2 matching pieces) and then trimmed each of the halves to 11-15/16” wide.

Step 3: Assembling the Pieces and Cutting the Partitions

I then assembled the 6 “blocks”. In each case, long pieces went on the top and bottom, 6” pieces went on the left and right, and 6-3/8” pieces went in the larger grooves. I drilled pilot holes and then screws in each of the corners (through the top and into the 6” side pieces, then flipped over and did the same on the bottom). On the two largest blocks I also drilled pilot holes and then screws through the top (and bottom) into the 6-3/8” partitions. I then sanded the 6 blocks (particularly the plywood edges).

Cutting the thin partitions
I then cut 9 partitions (each 6-5/16” x 11-15/16” from the MDF). These should fit nicely into the smaller grooves and be pretty easy to slide in and out (so that the animals can have single or double compartments as determined by the kids). As noted above, I also left some of the wider partitions unscrewed to provide flexibility in compartment sizes.
I then stacked up the 6 blocks and then kids loaded their animals. Note: I designed it so that the two 15.5” blocks could stand vertically (as in the photo) or horizontally as one layer (15.5+15.5=31).