Cut 2″ foam so it fits snugly on the top 
Defrost the machine. Cut 1″ foam to fit on 3 sides. Slide foam in place
Block makers lose their insulation over time due to saturation. The piece of foam under the blocks weighs less than 10lbs when installed. After years of use it can weigh over 150lbs because it holds the water. Adding your own foam can help a slow machine make ice faster.