STOP RIGHT THERE!
There's no reason for you to bother laying down the fleece like that, in fact don't even bother with the fleece. Throw it in the trash, and go down to your nearest walmart and buy the thinnest spandex you can find. As well as that it's not necessary to lay anything like fleece down when you just need a piece to fit the contours of your trunk. You've already got a mold so use it your advantage and lay the fiberglass down over the taped up and covered carpet. You'll get a perfect fit that's much stronger than some resin soaked fleece.
Order up some different grades of fiberglass. I don't know how many curves your planning on doing, but if it's anything complex don't plan on being able to use you typical 6 oz. fiberglass weave on it. You'll want something more or less around 2 oz. So start off with 2 oz. 3 oz. 4 oz. 5 oz. and your garden variety 6 oz. Take thread fill into consideration and move from your heaviest fiberglass to your thinnest before your final layer, and you'll minimize filler work.
Remember to use weave fiberglass on any part with curves, and for the more complex curves go to a lighter grade of fiberglass.
For the very bottom of the subwoofer box you could get away with using matte fiberglass (looks like interlaced shards of glass) since it is a fery flat surface. In fact I'd more then likely recommend you use matte fiberglass for the bottom since it's such a flat surface, bot for the sides of the box be sure to use weave fiberglass.
One more thing to keep in mind would be to use multiple layers of fiberglass for strength. In a sub box you want strength, and you simply can't rely on resin soaked fleece for strength. Lay down a thin layer of spandex and cover it up in a resin for your shape, and then move straight up to multiple layers of fiberglass. Make sure you lay down multiple layers of fiberglass!!
The only other tip I could give you would be to go down to your nearest hobbystore and buy some cyanoacrylate glue and kicker. Use it to secure your spandex to the wood frame. There's no point in covering up staple holes when staples arent necessary.