A simple method of controlling the draft and providing good circulation of gases in and out of the oven interior is shown here.
Tiles, or slices of firebrick are placed so that the bottom of the oven door is raised above the hearth. With the door set away from the plane of the oven mouth, the draft is controlled. This works especially well once the fire is well established as the chimney is already inducing draft.
The door and slot below can be infinitely adjusted by changing the thickness of the tiles and the distance the door is set from the face bricks.
Doors are also needed to keep the heat in for smoking and for heat retention. However, during a firing, the combustion of the wood needs to be kept steady and clean. Adjusting the door gap to match the quantity of wood in the oven will result in steady climb of interior temperature.