Vince Heuring wrote:

14x14x12 before upholstery and feet. So they will slide under the
glass-topped coffee table when not in use.

Yup. See the first line of my original post. I'm hoping to get rid of
a bunch of plywood and other scrap in this project.


Based on the above, I'd probably use 3/8" (At least 3 ply)or 1/2"
plywood(At least 4 ply).

Use box joints for the vertical corners and a rabbit for the top and bottom.

This will insure that all corners are 90 degrees and everything is
square if you glue up the entire box in one shot.

Once the glue has set, break all sharp corners with a sander and 40-60
grit paper, then as Norm would say, they are ready for the finishing room.

HTH

Lew