On the parchment paper, trace a pattern of the are of the switch plate that will be covered. Again, warm each slice to ensure it is soft. Press slice between your fingers to even out the cut. Place all pieces on the pattern to cover switch plate, pressing each of the pieces together as you go along. Smooth out any rough areas with your fingers and a brayer.
Transfer slices to switch plate from the pattern.
Smooth again to make certain seams don't show and surface is even. With small knife, trim any access from edges of the switch plate. Bake at 265 degrees for 25 to 30 minutes. Remove from oven and let cool. If the clay does not stick to the switch plate, remove clay pieces and apply adhesive to the back.