Stone has suggestions on how to do it on their website:
"During aging, chill the beer down to about 35°F or so, and let it sit until the beer clarifies. This is the step where the French Oak chips are added. Place the chips in a filter bag with a small piece of stainless to weigh it down and keep it from floating. Sterilize the entire bag and contents by pouring hot (over 185°F) water over the bag and letting it sit submerged for 15 minutes. Then hang the bag in your fermentor until the whole bag is submerged. Start tasting your beer after 3 days and age as long as needed after that to get the intensity of French oak flavor you want."
Personally I like using oak cubes (which have less surface area) and aging the beer longer. It is a personal taste thing, but if you liked their beer I would follow their instructions.