Make-ahead tip: Store in a cool, dry place up to 1 month. Prep: 1 day, Dry: 24 hrs.
Sprinkle cutting board with cornstarch.
Knead 1/4 cup gum paste at a time with a tiny drop of creamy peach paste food coloring, adding more food coloring a little at a time, if necessary. Roll gum paste to 1/8-inch thickness. (Cover remaining gum paste.)
Cut out 1 petal of each size with 1 1/2-inch, 1/2-inch, and 1/4-inch cutters. Lightly dust coated doubled-sided mold with cornstarch; press each petal into mold. Return large petal to bottom half of mold. Lightly brush center with gum glue; top with 1/2-inch blossom. Brush center with gum glue; top with 1/4-inch blossom, pressing center of stacked blossoms together. Remove and place on flower forms to dry. Repeat, making 4 dozen blossoms.
Repeat rolling and cutting gum paste procedure using 1-inch and 1/2-inch cutters. Return 1-inch petal to bottom half of mold. Lightly brush center with glue gum; top with 1/2-inch blossom. Gently press center; fold in half, and pinch bottom together, forming a bud.
Beat powdered sugar, meringue powder, and 2 to 3 tablespoons warm water at high speed with an electric mixer until soft peaks form. Stir in a tiny drop of buttercup yellow coloring.
Insert a coupler into a decorating bag; fit coupler with metal tip #14, and fill with powdered sugar mixture. Pipe a small dot of mixture in center of each peach blossom; insert 5 to 7 stamens in icing. Let dry 24 hours.
Knead 2 to 4 tablespoons gum paste with a tiny drop of juniper green paste food coloring. Roll out to 1/8-inch thickness on a surface lightly coated with cornstarch. Cut out leaves with leaf cutter. Press onto leaf mold. Place leaves in flower forms to curve; let dry 24 hours. Repeat until you have 4 dozen leaves of each size.
Cover and store in a cool, dry place.