We start by cutting a 1/2" veneer plywood base 8 1/2" X 11".
For the sides and dividers I used Fir MG Beaded Ceiling Tongue and Groove, 5/8" X 6" X 7'.
Cut two pieces 12 1/8" long with a 45 degree cut on both ends. Be sure to keep the tongue and groove details matched for each outside piece.
Cut two pieces 9 5/8" long with a 45 degree cut on both ends. These will form the outside of the box. You might want to match them up to your base and trim as necessary.
You could eliminate the 45 degree angle and butt joint the pieces but the 45 looks a lot nicer.
Cut two dividers 6 1/8" long and one divider 11 3/8" long.
Cut these three divider pieces down to 5 5/16" high.
Set your table saw with a 9/16" wide dado blade to cut a 3/8" deep groove.
On one 12 1/8" side cut two grooves. One 4" from the end and the second 8 1/2" from the same end.
On the 11 3/8" piece cut two grooves. One 3 5/8" from the end and the second 8 1/8" from the same end.
On the two short ends, 9 5/8", cut one groove 2 3/4" in from the end. Be sure to mirror the two parts so the beading of the wood is on the same sides.
Before putting the pieces together I stained them separately.