Acrylic manufacturer

[sphelps]

You should be about to source 1/4" cast pre cut with jointed edges for around $5-6 per sq foot.

For 18x18x20

Front and back = 18x20
Bottom = 18.125x20.125
Sides = 17.5 x 20 (x2)
Divider = 17.5 x desired height.

The bottom is a little bigger so you don't end up with the seam right on the edge or overhanging, that can be problematic for the glue. You do the same idea for the sides, sit them slightly inwards and directly on edge. The can router off excess material with a trim 3 flute bit.

The glue or solvent you want is weldon 4