You can freeze sugar cookies with royal icing, but it's essential to follow specific steps for the best outcome. Ensure the royal icing is completely dry before freezing. To prevent sticking, place parchment paper between the cookies and store them in an airtight container or bag, with layers separated by parchment. Label and date the container for reference. When ready to enjoy, thaw the cookies slowly in the refrigerator or at room temperature, avoiding heat or moisture. If the icing loses some shine or firmness, you can refresh it with water or fresh icing. Keep in mind that the icing's texture and appearance may slightly change after thawing, so consider freezing the cookies unfrosted and decorating them later for a fresher look.