Decorate like a pro—without a pastry bag. Spoon your favorite homemade frosting or purchased ready-to-use variety into a zip-top plastic freezer bag. (Do not seal bag.) Snip a hole in one corner of the bag. Pipe desired shapes or letters onto brownies, cakes, or cupcakes. For best results, we recommend practicing a few shapes on wax paper to find the perfect one and to get a feel for working with the bag and frosting.