Outline each shape with a thin line of piped royal icing. Allow the icing to dry.
Thin the remaining royal icing with water until a small amount dropped back into the bowl from the tip of a spoon flattens back into the surface in 10 seconds. Color the icing as desired.
Fit a piping bag with a #2 plain tip. Fill the bag halfway with the royal icing. To fill the outlines with icing, begin at the edges of each one and work toward the center. At the edge of the shape, hold the tip a short distance away from the piped outline and allow the icing to flow toward the outline, creating a rounded edge. Continue piping, allowing each successive pass of icing to flow into the previous one, creating a smooth surface.
Place the shapes under a heat lamp or other heat source to dry. The more quickly the icing dries, the shinier the finish.