Lightly dust a smooth work surface with confectioners' sugar to prevent sticking. Roll out fondant to the cake's size. To keep fondant from sticking lift and move it as you roll.
Gently lift fondant with rolling pin to move. Position it on cake.
Beginning in the middle of the cake, smooth fondant outward and down the sides to shape it. Trim off excess with a spatula or pizza cutter.
Use cookie cutters to create diamond shapes in the rolled-out fondant.