To the bowl of a stand mixer add 1 cup of your sourdough starter and 3 cups of room temperature water and mix until milky looking.
Mix in the flour until combined. Let the dough rest for 30 minutes.
Add the salt and 1/4 cup of the remaining water. Mix the dough until everything is combined and the dough comes off the side of the bowl. The dough will still be quite sticky and wet. Transfer the dough to an oiled bowl.
Now it's time to stretch the dough. With the bowl in front of you, picture the dough as if it were a clock with 12 being in front of you. Grab a handful of the dough (fingers under the ball and thumb on top) at 12, pull/stretch the dough then fold it back on top, like closing a book. Do it again for 3, 6 and 9 o’clock.
Cover the dough and let it rest for 30 minutes in a warm, draft-free spot. The microwave is a good place.
Repeat steps 4 and 5 three more times. For a total resting time of 2 hours.
After doing the stretch and fold technique 4 times (every 30 minutes for 2 hours), cover the dough with a clean tea towel. Let it rest in an undisturbed, warm, draft-free place for 2 hours or until doubled in size.
Slightly flour a clean countertop and put the dough on there. Cut the dough in half and shape each half into a large ball. Let it sit uncovered on the counter for 30 minutes.
Get our two proofing baskets, plastic or glass bowls. Flour them with a bit of flour or put a piece of parchment paper in there and put the bread on that. This will make transferring the dough to the Dutch oven easier tomorrow morning.
After the 30 minutes are up, do the stretch-and-fold technique one last time and transfer the dough to the prepared bowls.
Put a Dutch oven in the oven and preheat the oven, with the Dutch oven in there, to 425 °F (218 °C). I use a 7-quart Tramontina Enameled Cast Iron Round Dutch Oven.
Once the oven is preheated, take the Dutch oven out of the oven and put the bread in. If you used a proofing basket, gently tilt the basket and the bread will fall out into the Dutch oven. Or you can transfer the dough into your hand, gently, so that you don’t squish the air bubbles and put the dough in the Dutch oven. You could also use parchment paper - lift the dough by holding the parchment paper edges and put in the Dutch oven with the paper.
Score your bread with a sharp knife or a blade. Make 2 or 3 scores on top
Bake, with the lid on, for 20 minutes.
Take the lid off and cook for another 15 to 20 minutes.
Remove the Dutch oven from the oven, and remove the bread from the Dutch oven. Transfer it to a cooling rack for 15 minutes before slicing.
Put the lid back on the Dutch oven and put it back in the oven to re-heat for 5 minutes. Then repeat steps 3 to 7 for the second bread.
Baking the bread one loaf at a time allows them to bake more evenly.
When you do the stretch and fold technique, the first time the dough will be sticky and the last time you do the stretch and fold the dough will be softer and more elastic.