To make a flat cake, many folks cut the domes off after baking and cooling. Then you can take those domes and crush them up into cake crumbs. Use the crumbs to decorate the cake all over by holding the cake at an angle and pressing the crumbs into the sides of the cake. You can also use a cardboard template to make designs on the cake. Place the template onto the top of the cake, add a thick layer of crumbs and press down gently, lift the template straight up, and clean up your edges if necessary. Voila, decorating with crumbs!