Trim tops of all cake layers to make each 1½ to 2 inches tall. Place a 12-inch layer on a 14-inch silver wrapped cake drum or 16- to 18-inch cake plate/stand, using a small amount of buttercream to secure it to the board. If the cake needs to sit on a smaller board for space or to transport, build onto a 12-inch board instead.

Pour Vanilla Simple Syrup into a squeeze bottle, and generously soak cake layer.

Spoon buttercream into a pastry bag, and cut a ½-inch opening in tip. Pipe a border of buttercream around edge of cake layer. Spoon 3 cups (645 grams) Strawberry Cream Filling onto cake layer, and spread within border. Repeat with second cake layer, soaking layer with syrup and topping with remaining filling. Top with final 12-inch cake layer. Spread a thin layer of buttercream on top and sides of cake, scraping off excess. Refrigerate until frosting is set, at least 20 minutes.

Repeat entire procedure with 9-inch cake layers, building on a 9-inch cake board and using 1½ cups (323 grams) filling between each layer, and 6-inch cake layers, building on a 6-inch cake board and using ½ cup (108 grams) filling between each layer.

For sheet cake, place 1 cake layer on a 13x9-inch cake board; soak with syrup. Pipe a border of buttercream along edges, and fill with Strawberry Cream Filling. Top with second cake layer, and spread a thin layer of buttercream on top and sides of cake. Refrigerate until frosting is set.

Remove 12-inch cake from refrigerator. Spread buttercream on top and sides of cake, using an offset spatula or bench scraper to smooth. Mark center of 12-inch cake with a 9-inch cake board. Using a wooden pick, score perimeter of cake board. Insert a wooden dowel into center of 12-inch cake, and mark where dowel meets buttercream. Remove dowel, and use as a guide to cut remaining dowels to same length.

Insert 3 prepared dowels about 1 inch apart from each other in very center of 12-inch cake. Arrange remaining 6 dowels equidistant around center, about 2 inches away from scored circle. Return cake to refrigerator to set.

Repeat scoring and doweling process on 9-inch cake using a 6-inch cake board to mark center.

Using frosting for decoration, pipe designs on outside of cake layers and sheet cake as desired. When not decorating, keep cake layers refrigerated.

Place 12-inch cake tier, with cake board, on desired cake plate. Stack 9-inch and 6-inch tiers, with the boards they are on, on top. Let tiered cake and sheet cake stand at room temperature for 1 hour before serving.