Spray pan with vegetable pan spray. If desired, line pan with plastic wrap. Prepare crisp rice cereal treats mixture; press into pan. Unmold onto foil-wrapped cake board.
Spatula ice leaf area smooth; score leaf lines with edge of spatula. Flatten spice drops with your fingers to make flower petals; use 5 for each flower. Attach to tree with buttercream. Add white spice drop for flower center. Attach spearmint leaves.