Hi Roddy,
The bee-hive oven is pretty simple to make, but takes a while. Start with a good level foundation - bricks, cement or clay and make a 4 ft. diameter circle of clay and water about 6" thick. Build a mound of moistened dirt or sand about 3 feet high on this base. Wrap with wet sacking to retain the shape.
At this point, you should make a square door frame from brick of a size appropriate for what you plan to use it for. Stick a 8-10" long, 3-4" diameter tubular piece in the mold at the top back opposite the door. Cover everything with at least 4" to 6" of a thick clay and water mixture, called adobe in the U.S., or a mixture of stone, brick and clay mortar. Straw or hay may be added to the clay mortar for strength. Smooth the outer surface, cover it with dampened cloth, burlap etc and let it dry for days, then remove the cloth and let it dry some more. Then remove about 1/2 the dirt and build a small fire and maintain it for several hours. Then remove the rest of the dirt and build another small fire and maintain it for several hours. You want to gradually heat the whole mass, but slowly enough that it does not crack. All you need now is a door, which can be made of wood.
When the oven is thoroughly cured, you fill the interior completely with wood and build a fire. When the wood is consumed, removed the coals, sweep out the ashes and put the food in. Plug the top vent, close the door and wait until the food cooks.
Have fun,
Smoky