To a bowl, add all-purpose flour, bread flour, and salt. Mix with your fingers to combine.
Add sourdough starter, fed and grown to its peak, on top, and add 539g of water.
Mix with your hands until it comes together. Then start folding the dough over itself, then turn the bowl a little and repeat.
When you have a cohesive dough, gauge it. If it's very wet and soupy, don't mix in the rest of the water; if it can take more, add more water in stages until you feel like it's cohesive but pretty wet.
Once you're happy with the dough, you should see the first signs of gluten development.
Add exter-virgin olive oil on top and fold that into the dough.
Leave the dough to rest for 30 minutes under a damp dishtowel.
Bulk Fermentation
Now it's time to do three sets of stretch and folds spaced out by 30 minutes.
If you don't know how to stretch and fold, look at how I do it in the companion video.
Grab your roasting pan and smear it with olive oil.
After finishing the last set of stretch and folds, add the dough to the roasting pan. Press the dough out into the corners and stretch it as far as it goes without tearing it.
Put a damp towel over the top and let the dough rest for 30 minutes.
Over the next hour, do two more stretches to get the dough as close to the corners as possible.
Then, let the dough rest until it's appropriately fermented, bubbly, and light. It took about two hours at around 21°C/70°F for me.
When there's about half an hour left of fermentation, turn your oven to 230°C/450°F. I used fan assist.
Dimple and add toppings
When it's finished fermenting, grab the dough and gather all your toppings.
Dimple the dough with your fingers. Press down all the way to the pan.
Then, splash one to two tablespoons of olive oil over the dough.
Add all the toppings. Pushing larger toppings into the dough so they won't fall out after the bread has finished baking.
Bake
Put the pan in the oven and bake for about 30 minutes.
If your oven heats unevenly, invert the pan about halfway through baking.
When the end of the bake is nearing, keep an eye on the dough and take it out when it's sufficiently browned. If the bread isn't brown enough at 30 minutes, extend the baking time until it looks done to you.
Leave it to cool for a couple of minutes, remove it from the pan, and put it on a wire rack.