How to Cut a Layer Cake
Cut a four-layer cake with a long, serrated knife. Hold the knife horizontally, put one hand on top of the cake and slowly rotate the cake, cutting into the cake all the way around. Continue to rotate and cut deeper into the layer until you cut through and create two even halves.
You can also use a piece of thread rather than a knife. Hold a long piece of thread between your hands and start from the back. Slowly and evenly pull the thread through to the front.