Make daffodils 1 day in advance. Prepare royal icing following the recipe directions. Tint icing yellow. Attach the daffodil template to the flower nail and use a dab of icing to attach the flower square to nail with the template. Use tip 104 with a cut disposable decorating bag (with a coupler and yellow icing) to pipe daffodil petals onto the flower nail.
Change tip on bag and use tip 3 to pipe the flower center. Change tip and use tip 1 to pipe a zigzag around the flower center. Let dry overnight.