sand down the surrounding area take out whatevers behind it. mix some of the epoxy up and fill th eedges..then you can add more because its sandable. smooth then paint. if you can get a piece the size of the opening then that would be ideal. If not your gonna have to use strips until it covers up completely. you could do other things like use tape to build a surface the use the epoxy to completely cover the hole but thats a last resort the stuff is very durable but its more rubbery then the bumper material.

just to give you an idea of what it can be used for. molded 8 inch monitor also just finished molding the a/c control cover to the center console. I also covered up the cigarette lighter hole and relocated it to the passenger side cover.