Step 1: Attach Two Pieces of Plywood

Using a table saw or circular saw, cut a 45-degree bevel from the width of the plywood on one of the long sides.

Using drywall screws and a screwdriver, secure two right triangles of 3/4" plywood -- each 2' x 10" -- to two opposite sides of one 2' x 2' piece of 1/4" plywood. Secure the plywood rectangle between the heights of the triangles. The beveled edge of the rectangle must face up.

Step 2: Drill Slots

Using a plunge router and a 1/2" double-fluted router bit, drill about six 1" slots into the second 2' x 2' piece of 1/4" plywood. The slots should be about 1" apart.

Step 3: Attach the Slotted Plywood

Screw the slotted piece of plywood to the top of the triangles.
Use a jigsaw to drill a hole in the back of the rectangular piece of plywood. The hole must be just large enough to accommodate a vacuum hose.