Around 8 am mix together the three flours and 220 g of the water in a large bowl. Cover and leave at room temperature for an hour.
Add the starter to the dough and mix by hand until fully combined. Cover and let rest for half an hour.
After half an hour add the salt and the remaining water. If the dough is already pretty wet you don’t have to add the extra water. Stretch and fold the dough to combine. Let it rest covered for half an hour and then stretch and fold again every half hour for two hours ( 4 more sets of stretches)
After the last stretch and fold let the dough rest covered for two hours at room temperature. When it’s ready you should see a couple small air bubbles.
Tip the dough onto a floured counter and gently reshape it into a round. Let it rest uncovered for 10 minutes and prep your banneton by dusting it with flour. If you don’t have a banneton you can place a clean kitchen towel in a loaf plan and dust the towel with flour. Shape the dough into a loaf or a round depending on the shape of your banneton (shape into a loaf for the loaf pan!). Check out my other sourdough recipes for pictures of this. Cover the shaped bread and let it rest at room temperature for 2 hours.
Move the dough to the fridge and preheat the oven with the dutch oven in it to 450 F. If you don’t want to cook the dough in the next half hour you can just let it rest in the fridge for longer and preheat the oven half an hour before you’re ready to bake.
Once the oven is ready turn the dough out onto a piece of parchment paper, dust it with flour and score with a sharp knife or a lame. Place the loaf in the dutch oven, cover and bake for 20 minutes. Uncover after 20 minutes and bake for another 20-30 minutes until deeply golden.