Ive wanted to do this, because i have the same problem, and it makes me realize after ive been informed why its like 15-20 bucks in store
what ive been told they hvae to do is to soak the wood for months, changing water to get all the baddies out, other people have told me they boil the wood, then let it cool, then boil, etc etc a number of times until they believe its safe, they do it this way because they reckon the wood expands then contracts and every thing comes out of the wood.
dunno man, someone else on here would be able to explain the exact way, its just a pain, coz i live at the beach and there is always wood that i would put in there, i just cant be arsed.... lol