Use a long serrated knife to trim the tops of the round cakes flat, if needed. To get the smooth look of our cake, first stack the three cakes on a wire rack over a cookie sheet. Heat 3 cups of the yellow frosting in the microwave until it liquefies, about 20 seconds. Stir the frosting, then slowly pour it over the top of the cakes, as shown, covering them completely. Refrigerate the stack for about 30 minutes to harden the frosting.
Meanwhile, frost 12 of the cookies light blue and place a Twix in the center of each. Use scissors to cut the ends from the marshmallows and press on these ends, sticky side down, for wings.
Carefully transfer the cake to a platter. To add a door, trim one edge of the remaining cookie, as shown, cover both sides with chocolate frosting, then press it onto the hive. Spoon the rest of the yellow frosting into a resealable sandwich bag, snip off a corner, and pipe markings onto the bees and hive. Top the hive with the gumdrop and arrange the bees around it. Serves 12.