How-to Create Simple Frosting Finishes
Peaks: Smooth frosting over the top and sides of cake. With a tablespoon or icing spatula, press a flat side into the frosting and pull straight up, forming a peak. Repeat over top and sides of cake.
Waves: Use the back of a teaspoon or tablespoon to make a small twisting motion in one direction. Then move the spoon over a bit and make another twist in the opposite direction. Repeat until entire cake is covered.