Wet-on-wet cookie decorating is a technique where you apply a layer of wet icing to a cookie's surface and add additional wet icing in contrast colors on top of it while it's still wet ^{5 1 2 3 4}. Here are the steps:

1. Prepare your icing in different consistencies (stiff, medium, and flood).
2. Test the icing consistency.
3. Color your icing.
4. Create an icing "dam" around the edges of the cookie.
5. Flood the cookie with icing.
6. Add your designs using wet icing.
7. Allow the cookies to dry and finish.