1

If you are flavoring the syrup with orange zest, use a paring knife to cut the zest from the oranges, leaving as little of the white pith clinging to it as possible. Put the zest in a saucepan with enough water to cover, bring to a boil, and cook for 2 minutes. Drain and repeat.

2

Put the blanched zest in a saucepan with the simple syrup, bring to a simmer, cover, and let simmer for 15 minutes. Set aside to cool. Add the Grand Marnier to the cool syrup, whether it has been infused with orange zest or not.

3

Cut a cardboard rectangle 5 1/2 by 11 1/2 inches. Use this as a template to cut 3 rectangles crosswise from the sheet cake.

4

If the rectangles have hard crusts, trim the crusts using a serrated knife.

5

Stack the rectangles on the cardboard and trim all around until the sides and ends are even and there is a 1/4-inch border around the cardboard. Set the trimmed cake layers aside.

6

Place 1 cake rectangle on the cardboard and brush it with the flavored syrup. Keep brushing until syrup comes up around your finger when you press on the cake.

7

Cover with about one-third of the apricot glaze.

8

Spread about 1 cup buttercream over the glaze with an offset spatula. There should be a little oozing out the sides.

9

Place a second layer on top of the first and repeat the syrup, glaze, and buttercream. Then add the third layer and repeat.

10

Spread the remaining buttercream over the top and sides of the cake with an offset spatula. Allow a fairly large amount to droop over the sides.

11

Continue smoothing the top and sides, taking turns between top and sides, until the cake is perfectly smooth.

12

If you like, make a zigzag pattern in the frosting: Hold a serrated knife over the top of the cake on the end farthest from you. With the blade against the top of the cake, slowly pull the knife toward you while moving the knife gently from side to side.

13

Pipe any remaining buttercream around the top and bottom of the cake with a pastry bag fitted with a fluted tip.

14

To make round and separate rosettes, lift the bag up after squeezing out each rosette; for a wavelike effect, move the tip away from you while squeezing. Garnish with flowers, if you like.

15

Decorating a cake with fresh flowers: While fresh flowers are the easiest and perhaps the most elegant cake decoration, try to buy edible flowers from a food store, not the florist.