In this tutorial I'll show you how to make a Mad Hatter's Hat Cake Topper. It can be used as a decoration or a top tier. If you want the hat to have cake inside, simply substitute the polystyrene with cake.
13.
Use a clean, dry knife to cut the excess of the paste off. If you notice that the knife is pulling the paste (damaging the shape of the circle) that might mean that the blade was not clean/dry or that you didn't apply glue near the edges or that you applied too much glue (and the paste is sliding around).