In a large bowl, mix together the cake mix, water, eggs, and oil. Pour the batter into the prepared cake pan and bake for 25 to 30 minutes. Let the cake cool completely before using, about 30 to 60 minutes. Flip the cake upside down on a cookie sheet and trim ¼-inch off all four sides. Thinly slice off the bottom layer, approximately ⅛-inch or less.
Freeze balls for no longer than 10 minutes. Remove balls from the freezer and roll them again to remove any flat spots. Add the 12-ounce bag of light green candy melts into a Microwave safe bowl and melt until smooth. Add 1 tablespoon of Melting Aid and stir, until thinned out. Do not add too much.
Place the dark green candy melts in a piping bag standing up in a microwave-safe mug and heat at 30-second intervals until fully melted. Snip a small piece off the bottom of the piping bag so you get a thin opening. Pipe the green around the cake ball and quickly sprinkle the green sanding sugar and place a small red heart on the ball.