Stores like Wal-Mart set kits for about $8. You can use plastic bottles, bowls, just about any thing for a mold. Cut it to size and cover it with duct tape and petroleum jelly it help it break free after it sets up. The soft foam that is used in shipping packaging make a great tool to move and place the resin soaked mat. Wear thin rubber gloves with petroleum jelly on them, it helps to keep the mat from sticking to you. I've made my front brake ducts out of fiberglass using Mountain Dew boxes, duct tape, jelly and $8 kits. I had to cut a large hole in my trannie tunnel so the bell housing would clean. I made the patch with a 1 gal plastic ( 1/4 of it ) and a couple of kits. Black paint and you can not tell it was repaired. If you screw it up, just wait till it drys. Cut it out and do it again.
Dwight