Great question! Your jelly needs to be thickened but not set. If it's too runny, the liquid will drip straight off the cakes and the coconut will not stick. If it's been in the fridge for too long and has set, the jelly won't stick to the cakes at all. The jelly should be left in the fridge for 1-2 hours or until it's considerably thickened but doesn't turn lumpy when stirred.