Drain the wood chips. If your gas grill does not have a smoker box, place the chips in small aluminum foil tray. Cover the tray tightly with aluminum foil, then poke 8 holes in the foil with a knife to allow smoke to escape. Remove the cooking grate on one side of the grill, and place the tray directly on the heat plate (the triangular pieces). Replace the cooking grate. Light all of the burners, close the lid, and heat over medium heat until the wood chips are fragrant start to smoke, 10 to 15 minutes. Open the lid, reduce the outside burners to low, and turn off the center burner(s). Place the turkey over the unlit burners. Adjust the heat as needed to maintain a temperature of 225 to 275°F.