Glue onto carton bottom with frosting. Cut reserved piece into carton spout. Glue on carton. Insert skewer in spout to hold carton together until frosted. Cut diagonal slice off 1 end of each chocolate roll.
Frost cut ends together to form a curve.
Trim ends to taper. Place milk carton, books and banana on a wire cooling rack over waxed paper. Spoon on cake pieces to cover top and sides. Let dry at least 1 hour. Lightly dust with flour.