Step 2: Cut Grooves for the “Windows”
You can use a table saw or router for this, but I used a table saw. Set the blade only ¼” tall and set the rip fence ½” away from the blade edge.
Run your boards through the blade to cut small grooves like shown in the picture. It’s helpful to mark these before you go over to the table saw so you know where to cut.
If you have a dado blade that will cut ¼” on one pass, that’s great. But if you’re like me and you just have a single blade, then once you run them all through once, adjust the rip fence again so that it is about 1/8” further from the blade than it was on your first pass. This will make the groove wider and you should have a ¼” groove after the second pass on the table saw. Make sure your ¼” plywood fits in the grooves. If it doesn’t, you will need to adjust the rip fence again and make your groove even wider.