Cover the bottom of the rectangular dish with a layer of Graham crackers. You may cut smaller portions to fit. As you can see, I simply used the crushed grahams to cover the sides because I had lots of these. My wife told me later on that it's better to have cut smaller pieces instead because the crushed graham will be all over the place when you cut the cake. Use this only to fill-in gaps. She was right. So don't use crushed grahams as I did and cut up cracker portions as needed.