Part 3 of the Gumpaste Calla Lily tutorials, teaches

how to finish the flower. I suggest to use hear cutters for this step because they can be found easily.

Make sure your heart cutter is not too wide or your flowers will look to weird. 

Years after I made this video, Wilton came up with a Calla lily set for cones. Those will work well but the water cupswork really good too, Make sure you don't press on the cup really hard as you place the flower on it. If you do, you might run the risk of sticking the gumpaste to the cup, so as soon as you finish shaping the flower, test it to make sure it's loose and then move to the next flower.