First I cut out the place that mounted the cart, and then also the fingers for the manual. Next I cut a peice of 5mm thick art foam I purchased from Hobby Lobby, using double sided tape I stick it to the back of the case. This foam will be slightly thicker than the length of a normal DIP IC pin leg. Also it is easy to write on with a ballpoint pen.
I use the outside cover to put pinouts, chip info, and some basic schematics