Decorating Cookies with Royal Icing
Cut a small hole in the corner of a pastry or plastic bag. Insert a round tip; fill bag with icing. Hold bag at a 45° angle to the cookie, and pipe a bead of icing around the edge. Stop squeezing the bag before you lift the tip from the cookie.
Thin remaining icing so that it will flow smoothly. Fill another bag with thinned icing. Starting in the middle, fill in the cookie with the thinned icing, letting icing flow up to the outline. Let cookies dry overnight.
With a new small paintbrush, paint your own designs on the cookies with liquid food coloring.