After my wall was dried I installed the switches. To do this I had to cut a hole in the wood that matched the contours of the bottom of the switch. It had to allow the bottom of the switch to slip through but had to be small enough so that the lip of the switch didn't fall through too. In started by drilling regular circular holes in the wood and then used two files to shape it to the final hole. The top hole in the picture below shows the finished hole. The hole on the bottom is what it looked like before I I started filing.