Frost the cake with a thin layer of buttercream icing.
Knead the fondant until it's at a consistency that you're happy with.
Put confectioner's sugar on a flat surface and onto a rolling pin. Be careful not to put too much down, as this might dry out the fondant. Begin rolling out the fondant. Roll the fondant until it's a thickness you like and can easily cover the cake.
Roll the fondant over the rolling pin and gently unroll onto the cake.
Smooth out the cake with a smoother. Begin at the center top and work your way out to remove air bubbles. Continue down the sides. If an air bubble does occur, insert a pin at an angle to pop the bubble and smooth it out. Be careful not to pull or tug the fondant, as this might cause it to tear.
Trim excess fondant from the bottom of the cake with a sharp knife.
Cake With Corners
Follow Steps 1 through 4 above.
Smooth the top of the cake with a smoother. If there are any air bubbles, insert a needle at an angle and smooth over the bubble.
Pull the flaps of the corners away from the cake gently. This will prevent corner creases occurring on the cake. After you pull the flaps, smooth the area with your hand. Then continue to smooth the sides with the smoother.
Cut off excess fondant at the bottom of the cake with a sharp knife.
Smooth the entire cake one more time with a smoother.