"SBH" wrote:
I am building a plyometric jumping box using 3/4 plywood with about a
7 degree taper (to avoid tip over) with a platform size of 20 x 24.
There will be 5 total boards; front, rear, right, left and a center
for extra strength. I am thinking about dadoing the corners and the
center on the front and rear boards for the sides to slide into to
gain extra strength and stability as opposed to just butting the ends
together with glue and nails.

Another approach:

Cut two (2) identical trapazoidal shaped pieces complete with a slot
in the middle the width of the plywood thickness cut halfway thru.

Slot is cut from top on one piece, from the bottom on the other piece.

Now assemble pieces at the slots to form an intersecting cross, much
like an egg crate.

Fit a square piece of ply on the top and secure with glue blocks and
screws.

They won't stack but are simple to build, strong, and stable.

Lew