We'll need some sort of frame to support the switches during use. You can easily make one using square 3/4" x 36" dowels and wood glue.

Measure & Cut Dowels

Use a hacksaw or bandsaw to cut your dowel into the following pieces:

• 2 x 240mm length
• 4 x 55.5mm length
• 4 x 40mm length

Assemble

Apply wood glue to both ends of each 55.5mm piece of dowel and assemble them between the two longer 240mm pieces. Make sure to leave a 55.5m gap between each piece.

Clamp the frame together using clamps and allow the glue to cure - the glue I'm using cured within in an hour. Once the frame's glue has dried, remove the clamps and then move on to attaching the legs.

Apply glue to one end of each 30mm piece, secure them to each corner on the bottom side of the frame, clamp, and allow them to dry.

Mount Switches

Place each switch in one of the frame's square slots.  I used blue as Switch 1, yellow as Switch 2, and Red as Switch 3 and wrote some code to display corresponding colors on the Circuit Playground Express.