Step 4: Wooden frame
Assemble the frame except for the second side. Drill a hole on the spot you want the power cable to enter the clock (I made one at the back, right behind the spot where the Arduino would be, such that it is possible to connect and disconnect the USB cable from the outside even after closing the frame). Push four nails into the bottom of the foamboard frame on a distance from the front and back, equal to the thickness of the wood (see image). Now shove the foamboard frame, including the electronics underneath, in the wooden frame, make sure the electronics will not be able to move, and finish the frame.