Using a scale to measure, into a large ceramic or glass bowl add sourdough starter & water. Using the Danish dough whisk, combine well until no lumps of starter left.
Add in flour & salt and combine with the Danish dough whisk until as combined as possible. Then, using clean hands, knead the dough in the bowl until all flour is combined and hydrated.
Cover the bowl and sit at room temperature for 1 hour.
Remove cover from bowl, using clean hands, stretch & fold your dough. Cover the bowl again and leave to sit for a further hour. Repeat this process for 3 or 4 stretch and fold sets.
After the last stretch and fold, cover bowl and leave to bulk ferment on your counter for at least 8 hours, or until the dough doubles in size and is well fermented and jiggly.
Turn out the dough onto a lightly floured surface & divide into 2.
With each half of the dough, stretch into a rough rectangle shape, fold in all edges and then roll into a tight log.
Using your hands to cup the dough, pull it towards yourself while tucking the dough underneath itself to create surface tension. Turn the dough 90 degrees and repeat until the dough is a tight ball shape.
Place each ball, bottom side up, into a floured & lined banneton. Cover and place in fridge overnight or for at least 4 hours before baking.
When ready to bake, preheat the oven to 225 degrees Celsius (446F) with a Dutch oven with its lid on in the oven also.
Once the oven is preheated, remove 1 loaf from the fridge and turn it out onto some baking paper. Using a sharp lame, score the top of the loaf and add to the Dutch oven.
Bake for 25 minutes with the lid on, then remove lid and bake for a further 25 minutes or until the crust is a light brown colour and the internal temperature is around 96C (205F).
Remove loaf from dutch oven and onto a cooling rack. Let cool completely before cutting.