In advance: Make candy platforms. Using candy colors, tint portions of melted candy yellow, pink and blue. Place large Cut-Outs on non-stick pan and fill 1/8 in. high with melted candy; refrigerate until firm and unmold. Reserve excess candy.
Bake and cool 1-layer cake using firm-textured batter such as pound cake. Using medium Cut-Outs, imprint top of cake with squares and circles. Cut out at imprints using paring knife.
Cover cakes with reserved melted candy. Immediately insert toothpick in center of cake top to make a hole for flower pick. Attach cakes to candy platforms with melted candy. Remove toothpick; refrigerate cakes until firm. Roll out fondant 1/8 in. thick. For square cakes, cut 2 x 1/4 in. strips for sides and an 8 x 1/4 in. strip for top border; attach with damp brush. For circle cakes, cut dots with narrow end of tip 12 and an 8 x 1/4 in. strip for top border; attach fondant with damp brush. Insert picks.