Once the starter is bubbly and active, remove 100g sourdough starter and place into a large bowl.
Add in 325g of water and 500g all-purpose flour to the starter.
Give it a mix and cover with plastic wrap. In the meantime, microwave the 25g of water and add 9g salt and give it a stir to dissolve. Set aside.
30 minutes later, add in the salt water to the flour mixture. Use a spatula or your hands to give the dough a few kneads. Cover again and let rest.
Once every 30 minutes, give the dough a few stretches and folds with your hands. (Best way to do this is to wet your hands and pull the dough up gently; rotate the bowl 90 degrees and repeat).
Do this for the next 2 hours (for a total of 4 sets of stretches and folds) and then cover the dough, and set aside to bulk ferment.
My bulk fermentation for a dough around 78°F is about 4 hours.
Depending on how warm your kitchen is, this can take anywhere from a few hours to 10-12 hours. (It will rise slower than active dry yeast).
Once the dough feels ready (you can see lots of bubbles on the surface), and has increased in volume (but not necessarily double in size) it is time to shape.
Transfer the dough to a well-floured surface, and pinch the edges together so it becomes a round ball.
Using a dough scraper, push the edge of one side of the dough to create a bit of tension. Repeat with the opposite edge (eg. North to South, South to North) and then then East to West and West to East.
Place the dough seam side up into a banneton dusted with rice flour (my banneton is 6" in diameter). Cover with plastic wrap and let it rest at room temperature for 30 minutes.
Move the dough into the refrigerator to proof overnight (cold ferment).
In the morning, preheat a dutch oven/cast iron pot with cover to 500°F for at least 30 mins to 1 hour.
Remove the dough from the fridge and score with a sharp knife (this gives the bread a weak point for the steam to escape).
Transfer the dough onto a piece of parchment paper. Remove the banneton.
Carefully remove the hot dutch oven pot from the oven (use gloves) and place the dough into the pot with the parchment paper. Cover with the lid.
Place it into the oven and bake at 500°F for 20 minutes.
Reduce the temperature to 400°F and bake for another 30 minutes.
Let completely cool before slicing. (Cool for at least 3-4 hours).