you should really skim through the videos on youtube.... also search google for "homemade fiberglass speaker box"... or similar searches. there are several methods. one that i intended on doing myself was to use expanding foam. One you build a basic one-layer shell, you can cut it open and remove the foam. then put the halves back together and layer it all up. doesnt look too hard. just that you have to invest in a bunch of consumables because the resin ruins whatever it touches. sticks, cups, spreaders... etc...
try this one for example
(pic warning on this one)
good write up
the beauty of doing it yourself... if you decide to try again or make it better/bigger or something... you've already got some of the experience needed.