Once the fire gets going, add 2-3 pieces of wood so that the flame reaches the center and front of the dome, without lapping too far out of the oven opening. Use seasoned wood that is roughly 3’-4’ in diameter, and roughly 18’ long. Your firewood should not smolder or smoke before catching fire, and should burn easily and quickly. Once the fire is well established, continue adding more wood, and wait for about 20 minutes.
After about 20 minutes, a small spot at the top center of the oven dome should start to turn clear (or white), and then begin expanding outward. This "whitening" is the sign that dome is reaching the desired cooking temperature. This change occurs when the carbon accumulated on the oven dome reaches about 700ºF, and turns from black to clear.
The photos show the top of the dome starting to turn clear, then the sides, and finally a completely clear dome, ready for cooking.
Once the whitening has started, begin building the fire toward the walls of the oven by adding pieces of wood on either side of the fire, and in the back. This wider fire will help drive the necessary heat across the entire cooking floor, and evenly spread heat across the cooking dome. Within a few minutes, you will see the whitening spreading across the dome to the sides.
After roughly 45 minutes, the entire cooking dome will turn clear, and the cooking surface will have reached the desired 700ºF for cooking pizza, and you will have saturated your oven with the heat it will need for baking and roasting. You are ready to start baking pizzas, or you can let the oven temperature fall in order to start roasting or baking higher heat appetizers. Alternatively, you can rake out your coals, let your oven temperature moderate, and begin retained heat baking. For more details on different cooking styles, see Chapter 3. Types of Wood-Fired Cooking.
If you will be baking with a fire, or hot coals, you should push the fire to the side of the oven, not to the back. There are two good reasons for this. First, you can see the side of the pizza (or whatever you are cooking) and be ready to turn it when brown. It’s harder to do that when the fire is in the back. Second, your oven will cook better. Wood-fired ovens work by breathing in cold air through the lower part of the oven opening, heating it and circulating it around the oven dome, and then exhausting it out the top of the opening. By putting the fire in the back, you are giving the cold air a longer path before it hits the heat source, which is both cooler, and less likely to create a nice circular convection pattern.
Watch the Top Down Fire Video to see a really easy to fire your oven.