Cut the tip off a decorating bag and insert your choice of decorating tip. Use a small, medium or large decorating tip to make smooth spirals, or try a star-shaped or shell tip to make textured spirals. Fill the bag with royal icing for decorating fondant or crusting buttercream icing for decorating cakes iced with buttercream. Add just enough icing as needed to decorate the cake; twist the end of the bag and tie it just above the icing level.

Hold the bag so the tip is at the center of the desired space for the circle. If you want to cover a cookie with one large swirl, position the tip at the center of the cookie, for example. Hold the bag perpendicular to the surface on which you want to make the icing swirls. This means holding the bag vertically to decorate the horizontal top of a cake or cookie, or hold it horizontally to decorate the vertical sides of a cake.

Squeeze the bag with medium, constant pressure until icing begins to stream from the decorating tip. Make a small dot at the center point. Drag the tip out from the dot and around in a circle. Instead of closing the circle, drag the tip out again to make another circle around the previous circle, repeating this process until the spiral reaches the desired size. The space between each circle in the spiral should be to scale with the size of the swirl. Choose greater spacing when making a swirl to cover the top of a cake than when covering the top of a small cookie.

Stop squeezing the bag when you complete the spiral. Lift the tip straight away from the spiral to break off the icing string.