It might help to get it bolted on with a strong net lining that's about 6-8 inches off the ground. That's what they do at 688 skatepark. But yeah pretty much it's a big box with foam in it.
have your dad help you or something, look at some of the kicker plans on rampplans.org, and then make a big 15x15 or so wooden box and throw the foam in it.
yoo, if you live in nj and you like the foam at Tic, just go to tic more often, cause if you have enough money to make a good foam pit, then you probably have enough gas money to get to tic.