Use some laminating epoxy (FG is optional for 4” Diameter kits), and some Mylar. Smooth the epoxy under the Mylar to wipe out any air pockets. Don’t stress the excess epoxy drooling over your fins. Once everything is dry, use 80-100 grit sandpaper on a palm sander (heck, even a hand sander) to sand this all away. Make sure to wear a mask, glasses, gloves, and a long sleeve shirt as the dust gets everywhere. Have the shop vacuum close by!