In advance, use melted candy in cut parchment bag to make candy tree. Position pretzel in mold; refrigerate to set and unmold.
Press crisped rice cereal treats 1 in. deep in sheet pan. Unmold onto waxed paper sprayed with vegetable pan spray. Use medium round cutter from set to cut base. Place base on cooling grid positioned over sheet pan and cover with melted candy. Cut hole in center of base and insert Christmas tree.
Divide treat base into eights and attach confetti sprinkle garlands from division points with dots of melted candy.