Run-outs can be piped onto the cake or onto a piece of waxed paper which has been secured with masking tape to ensure that there are no creases. Draw the shapes onto the paper then pipe the outlines, which can then be flooded to fill the center with a smooth, slightly domed surface. Always use freshly made icing.
Pipe the outline with a #1 writing tip, following the marks on the waxed paper. Be careful not to make the icing too runny or it will overflow the sides and if it is too thick, it will not give a smooth surface. The correct consistency of the icing for flooding should collapse and lose its shape if the bowl is tapped.
Half-fill a waxed piping bag with soft icing, snip off a small hold and fill the outline shape or use a writing tip and fill the outline shape generously to make the surface slightly domed. Use a pin to coax the icing into the difficult areas and to break any bubbles as soon as they appear on the surface.
Allow the run-outs to dry for at least 48 hours before peeling away the paper. Stick on the cake with a little royal icing.