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When you want to frost the sides of the cake, you'll need to apply a thin crumb coat to the exposed cake, trapping any loose crumbs inside. Note that the cake will show through the crumb coating. You only want to use a thin layer of frosting to trap the loose crumbs. This layer will not be visible once the cake is complete. If your refrigerator is large enough, place the cake inside for roughly 30 minutes to help the crumb coat set. If you cannot chill the cake in your refrigerator, you should at least let it rest in a cool room for several minutes before handling it again. Consider placing a small fan in front of it to help the frosting cool. Ideally, the frosting should become so cool that it no longer feels sticky. Apply a thicker layer of frosting over the crumb coat of the cake. Continue until all sides are thoroughly coated and smooth. Before frosting the cake, slide strips of wax paper underneath the bottom of the cake, forming a square frame. Excess frosting will get on the wax paper instead of the cake board or platter. When you finish frosting the cake, you can remove the wax paper strips and the mess all at once. From this point on, you can apply any decorations you want using additional icing, candies, or non-edible embellishments. Once you've added the finishing touches to your decorations, the cake will be complete and ready to serve.
Apply a crumb coat. Chill the cakes again, if feasible. Frost the sides of each tier. Decorate the cake as desired.