Level tops of all four cakes. Place one 8-inch cake and one 6-inch cake on an 8-inch or 6-inch cake board. Trim any cake board that sticks out from the edge. Frost tops of cakes on boards and top with the second layer of cake for each tier.
Frost sides and tops of both 8-inch and 6-inch tiers, then center and place the 6-inch tier on top of the 8-inch tier. Border both cake edges with small black gum balls, chocolates, or jelly beans.
Place rock candy sticks in a large resealable plastic bag, and crush candy loose from the sticks with a rolling pin. Begin placing candy rock pieces around the cake, starting with the biggest pieces on bottom and using smaller pieces as you move up, as shown. Finish with black candies and plastic spider rings.
Toni Miller is the baker and author behind the festive dessert blog Make Bake Celebrate. She loves creating treats that look just as sweet as they taste, while helping others learn to create their own. When she's not working with buttercream and sprinkles, Toni has the privilege of serving as an Army wife and raising three sweet little girls.