Cut Plywood to Size
I used my Kreg Rip Cut to cut the 3/4" plywood to size. I sized mine for the largest type of saw blade we needed which meant 11 1/2" interior for us. I made it a perfect square, so had the top and bottom cut 1 1/2" longer. Sand if needed.
Drill Pocket Holes
I drilled two pocket holes per side to connect the plywood box.
Cut Grooves for Dividers
You could use a plunge router for this. I used my skill saw on a shallow depth and my Kreg Rip Cut for a guide. I cut four grooves for dividers in the top and bottom pieces of plywood.
Optional- cut grooves for backing (I did this but then took it out. I preferred it without.
Assemble the box using pocket holes. Be sure to line up your grooves front to back so you will be able to slide in your dividers.
Cut Acrylic Dividers
You could choose to route thicker grooves and use hardboard for your dividers. I used acrylic I had on hand. Cut acrylic by scoring with a utility knife and a straight edge (score a few times), then snapping it over the edge of a table.
Slide in the Dividers
Slide them in and it's ready to go! Sand down any rough edges showing using a fine grit sandpaper (I used 100)