Stacking three layers of cake is easy. Place your first layer of cake on a cake stand or cake plate. Add a thin layer of frosting on top of the cake then add your next layer of cake on top of that one. Add a thin layer of frosting on top of the second layer of cake. Finally, add your third layer of cake on top of the frosted second layer. Make sure to stack them as evenly as possible so that the edges line up. As you are stacking, I recommend stacking each cake layer with the top of the cake down and the bottom of the cake with its flat edge facing up.