In a bowl, combine confectioners' sugar and meringue powder and ¼ cup water.
Beat on low speed until soft or stiff peaks form (depending on the consistency you want), about 5 min. Scrape down the sides of the bowl regularly.
Add more water near the end to adjust the consistency for flooding versus piping.
Notes
Storage: If not using immediately, store in an airtight container for up to 3 days. This type of icing dries out quickly (and if it dries out in your piping tip it's a mess to clean up), so cover your piping tips with plastic wrap or a damp paper towel even if you are setting them aside for just a few minutes.Keep containers of royal icing covered tightly as well.