On a 13-by-11-inch cake board or serving platter, arrange the cupcakes into milestone birthday numbers (or the initials of the person you’re celebrating!). Plan to have about two dozen cupcakes on hand to work with and 6 to 8 cups frosting. (The cupcakes that are not used for the pull-apart cake can be frosted and served on the side.) Place approximately 1/4 cup frosting on top of each cupcake using two spoons. Use an offset spatula to smooth the frosting into an even layer across the cupcakes. Transfer 2 cups of the frosting to a disposable pastry bag or resealable plastic bag fitted with a star tip. Pipe stars of buttercream onto the surface of the frosted cake. Decorate with candy pieces and fresh edible flowers.