Splitting a cake into thin layers can make any baker nervous. When I began teaching, I looked for some sort of guide. It had to be something everyone has around the house. The answer turned out to be yardsticks. For best results, I recommend buying three yardsticks and splitting them in half to yield six 18-inch sticks, each less than ¼ inch thick. By stacking them one on top of another, you can vary the thickness of the layers you wish to cut.
To proceed, place your yardsticks equally on each side of the cake, back and front. You can place one yardstick on each side or stack two or three on each side, depending on the thickness you desire. Using the top stick as your level, rest a 12-inch serrated knife on the stick or sticks with your hand centered on the cake to steady it. (You will cut the layer bottom side first.) Saw slowly through the cake. The handle of the knife should be off the cutting surface to allow greater freedom of movement. After you have cut each layer, remove the top portion; if fragile, slide a removable quiche bottom under the just-cut thin layer and set it aside. Replace the uncut portion between the yardsticks. Be sure your knife rests on top of the yardsticks at all times to cut a level layer. Refrigerating or partially freezing the cake before you split it can facilitate your cutting the thin layers in this technique.