Make giant Wilton Rose 3 days in advance. Prepare royal icing following recipe directions. Tint coral. Use tip 127D, cut disposable decorating bag and coral icing to pipe giant rose on parchment paper square-covered 2.5 in. flower nail. Let dry, about 3 days.
Make layered cakes. Prepare batter following recipe directions. Bake two 10 in. cake layers, four 8 in. cake layers and one 6 in. cake layer. Cool cakes completely.
Prepare buttercream icing following recipe directions. Tint portion teal. Reserve remaining white. Level, fill and stack 8 in. cakes on same size cake circle for a 4-layer cake, 8 in. high. Level 6 in. cake and place on cake circle for a 1-layer cake, 3 in. high. Level, fill and stack 10 in. cakes on cake circle, for 2-layer cake, 4 in. high.
Use spatulas and teal icing to ice 10 in. cake smooth. Use spatulas and white icing to ice remaining cakes smooth. Reserve remaining teal and white icing
Decorate 6 in. cake. Use cake marker to mark cake 1 3/4 in. from bottom of cake. Use cake dividing chart and cake marker to divide cake into 12ths at both 1 1/2 in. and 2 in. from bottom of cake. Use tip 3, cut disposable decorating bag with coupler and reserved white icing to pipe dot border at 1 3/4 in. from bottom of cake. Use tip 103, cut disposable decorating bag and white icing to pipe scallops above and below dot border using 1 1/2 in. and 2 in. marks as guides.
Decorate 10 in. cake. Use tip 1A, cut disposable decorating bag and teal icing to pipe balls around bottom border of cake. Use 9 in. angled spatula to pull dots up. Repeat with a second row. Use tip 3 and white icing to pipe ball border above second pulled dots row.
Decorate 8 in. cake. Use bottom half of circle cutter to lightly imprint bottom of cake, marking scallops 1 1/4 in. tall. Make 10 scallops around cake. For second row, move cutter up 1 1/4 in. and mark scallops between scallops in first row. Repeat this four more times, making a total of six scallop rows.
Use tip 104 and white icing to pipe in scallop lines in void areas between first row of scallop pattern, moving up 1/4 in. each piped scallop and gradually decreasing width to stay within markings. Continue pattern with all scallop rows.
Finish decorating cake. Stack cakes. Use tip 3, cut disposable decorating bag and white icing to pipe bead bottom border of 6 in. cake. Use icing to attach rose.