• The process of baking bread starts 2-3 days before, as you need to have an active sourdough starter.  Feed your 100% hydration starter once or twice before preparing the overnight starter, if you keep your starter refrigerated. (I feed it twice, every 12 hours at a ratio of 1:3:3). (You can also consider taking some starter from a friend who has or buying from a specialized store, or making your starter from scratch. 

Prepare the overnight starter.

• In the evening stir down the 100% hydration sourdough starter, and remove 33 g in a bowl. First add the water and stir well. Add flour and stir.
• Cover with plastic wrap, and let it rest at room temperature for 12-14 hrs (overnight). 

Prepare the final dough.

• In the morning, in a large bowl mix the flours with water and the overnight starter until well combined. Let the dough rest (autolyse) for 30 minutes.
• Add the salt and knead by hand for 5-8 minutes.
• Wipe the inside of the bowl with a little vegetable oil. Place the dough into the bowl so the dough can be stretched and folded without removing it from the bowl. Cover with plastic wrap.
• Let the dough ferment at room temperature for 2.5 hours, stretching and folding on 4 sides,  every 50 minutes, using wet hands.
• Turn the dough out onto a floured surface. Divide it in two pieces. Shape them in the form of a ball. Sprinkle the balls with flour, cover  and let rest for 15 minutes.
• Meanwhile prepare two round bowls with 2 kitchen towels, sprinkled with flour, or use bannetons if you have.  Add the dough balls seam-side-up, cover them with the edges of the towel, and proof for 2 or 2.5 hours at room temperature. You will know it's done when pressing the dough with the finger, it comes slowly back.

How to bake the bread.

• Turn the oven to 470°F (240°C)  with either a baking stone or dutch oven or in case you don't have any, simply a baking sheet, and preheat for 45 minutes to 1 hour before baking.( If using the baking stone or the baking sheet place a small pot with water at the base of the oven to create steam, the dutch oven does not need as the lid will create enough steam.)
• Turn the proofed loaves onto a parchment and score them using a bread lame or sharp knife. Carefully transfer it to the preheated dutch oven baking stone or back of the baking sheet.
• Bake for 20 minutes with steam then remove the pot with water from the oven.  When using dutch oven simply remove the lid.
• Reduce oven temperature to 440°F (230°C)  and bake for another 15- 20 minutes without steam.
• Cool on a wire rack. Let them cool completely before cutting for at least 2 hrs.