I've posted this before, but here goes.
On the charcoal grate goes a ring filled with briquettes and wood chips.
Then directly over that a pizza stone sits on the cooking grate.
Then a 18" by 3" deep round cake pan sits on the stone. Inside the pan is a rack that sits about halfway up from the bottom of the pan.
Then water goes in the pan, and the food goes on the rack.
That was two untrimmed racks of spares that I fit in there. So far I have only used it for ribs, but I see a brisket in the near future.