1. Bake cake layers according to directions. Wrap layers in plastic wrap, and freeze 2 hours or up to 1 month until ready to assemble.
2. Cut domed top off each layer using a serrated knife, if necessary.
3. Cut 1 (6-inch) and 1 (8-inch) circle from sturdy cardboard; cover with foil.
4. Spread a small amount of Buttercream Frosting on 1 side of each cardboard circle, and place 1 of each corresponding cake layer on top. Spread top of 6-inch layer with 1 cup White Pearl Filling; spread top of 8-inch layer with 2 cups filling. Top with remaining corresponding cake layers.
5. Cut 4 wooden craft sticks or dowels to height of 8-inch tier; insert vertically into 8-inch tier about 3 inches from sides. (Space them evenly, and be sure they are level with top of tier.)
6. Spread tops and sides of 6-inch and 8-inch tiers with a thin layer of Buttercream Frosting to seal crumbs, working from top down and smoothing with a wet spatula. Chill at least 30 minutes or, if desired, up to 8 hours.
7. Place each tier on a wire rack over a large shallow pan.
8. Prepare Poured Fondant, 1 recipe at a time. Quickly pour fondant over cake tiers, completely covering tops and sides. Reheat excess fondant in microwave oven, if necessary. Continue until tiers are evenly coated. Let dry before decorating. (If necessary, touch up fondant with a hot, wet spatula before letting it dry.)
9. Position 8-inch tier in center of a 10-inch glass cake stand. Position a 4-inch glass plate on top of 8-inch tier. Invert a 3- to 4-inch glass candy dish, and position in center of glass plate, forming a pedestal; tie with ribbon, if desired. Top with 6-inch tier.
10. Insert a coupler into a large decorating bag. Fit coupler with metal tip #125, and fill bag with remaining Buttercream Frosting. Pipe a ruffled border around bottom of each tier. Pipe a reverse shell along top of ruffled border with metal tip #16. Replace bag with metal tip #2, and pipe scrollwork on sides of each tier.
11. Attach Royal Icing Flowers around top edges of each tier with a small amount of frosting. Pipe leaves between icing flowers with metal tip #352. Place a small cluster of fresh roses in center of 6-inch tier; scatter rose petals around top of each tier, if desired.