In a large mixing bowl combine the sourdough starter with 1/2 a cup water and 1/2 cup flour. Cover and let stand overnight or for 12 hours at room temperature.
Transfer to the bowl of a stand mixer fitted with the dough hook attachment. Add the remaining water to the bowl, dissolving the previous days mix before gradually adding the remaining flour. Mix until smooth and well combined. Transfer to a lightly oiled large bowl, cover with a clean towel and let the dough rest for 30 minutes to 4 hours.
Once the dough has risen, sprinkle in salt and then start to kneed. Grab the dough from one end, lift it up and fold it over on top of itself. Turn the dough 90 degrees and repeat the action for another 4 minutes. Place dough back in the bowl, allow to rest for 30 minutes and repeat process 4 more times.
The dough should now be light and fluffy, spin the dough on itself tucking the edges overlapping underneath creating a lovely circular strong dough.
Place a tea towel inside a bowl, dust with flour and transfer to a fridge and leave for overnight.
In the morning turn your oven to the highest temperature and place a medium dutch oven inside to heat for 20 minutes. Remove your dough from the fridge, bring to room temperature before turning into hot dutch oven. Slice two parallel lines 1 1/2 inches from each other.
Cover pot with lid and bake for 20 minutes before lowering temperature to 450 F, removing lid and cooking for another 25-30 minutes or until crust is deeply browned. Allow to cool at least 15-20 minutes before serving.