The flower pot will completely cover the grill, serving as the lid, and creating an "oven" of sorts. The pot already comes with a drain hole in the bottom, so I could affix a thermometer there. I'm wondering if this will create ventilation issues, though. I could always drill some holes in the sides of the pot, if necessary.
Also, I'm going to have to devise some way to hoist the thing on and off the grill, as I'm guessing it's going to get pretty hot. Perhaps I could leave it elevated just a bit off of the grill surface, and that would take care of the vetilation issue also.