Once your cookies are outlined and the icing has dried, you’re ready to start flooding!
Firstly you will need to thin down your left over icing, just add small amounts of water and stir in until the icing is thin enough to run off the spoon quickly. We’re aiming for a consistency closer to soup than to water. If it ends up being too runny, you can just leave it to one side to dry out for a little bit.
When it’s ready, load it into your piping bag or bottle and begin flooding. Start at the top, close to the outline and let the icing flow from the nozzle. You will want to move the nozzle around the cookie as you go but because this icing is now runny, you can leave gaps when you pipe as the icing will flow into any gaps there may be. You can always use a spare nozzle or something clean and pointy to help drag the icing into position.