1/2" baltic birch, 1/4" baltic birch, 1/8" divider material ( foam pvc in our case )
1/4" stock cutter, 1/8" stock cutter
Cut left and right support panels from 1/2" ply
1/4" cutter for most of the rabbets (0.1" cut depth)
1/8" cutter for the front and back panels
I did not add dog bones, so the internal corners will need a small chisel touch-up to clear out the rounded corners
Cut the base from 1/2" ply
The leading edge will need to be trimmed at 22.5 degrees
Cut the left and right slots from 1/2" ply
To properly support the dividers, a 1/8" cutter is needed to reach the bottom of the slots. The slots could also be made from thinner material to necessitate fewer passes and speed up the cut time.
Cut front and back from 1/4" ply
Trim the top and bottom of the front piece at 22.5 degrees.
Cut 4 dividers from 1/8" material of your choice.
If desired, you can use the single line alphabet font to engrave the sandpaper grits into the dividers' tabs.
Dryfit / Glue
Dryfit: Double-check that the 22.5 degree trims are aligned correctly, and that the left and right slot elements are aligned correctly.