Combine the flour, starter and water in a mixing bowl fitted with a dough hook or in a bowl if mixing by hand. Mix till just combined and let it rest for 20 to 30 minutes (this is called autolyse, which helps the doughs structure but isn't strictly necessary).
Add the salt and continue mixing of kneading until the bread is soft and smooth and pliable, 1o to 15 minutes.
Cover the dough with plastic wrap and refrigerate overnight or for up to 48 hours.
Several hours before you intend to bake, remove the bread. Remove the plastic and cover the bowl with a towel. Let the bread warm up for an hour or so.
Remove the dough from the bowl. (If you want to see how lively it is, cut it open--you should see a network of bubbles; if you don't, your bread won't rise; throw the dough at your neighbor's house as a primitive form of greeting.) Press the air out and kneed it a bit to move the yeast around to a fresh food supply. Shape the dough into a tight boule by rolling it back and forth and around between your hands.
Put the dough in a parchment lined bowl, cover it with a towel and let it rise until you can just stick a finger into the dough and the indent is not quick to bounce back. This can take 2 to 5 hours depending on your dough (remember, it's alive, and everything alive moves at its own pace).
Put a Dutch oven in your oven and preheat to 500˚F.
When the ovens are hot, rub the top of your dough with some olive oil. With a sharp knife, cut a hashtag in your dough and say "hashtag sourdough!" Using good mits or hand towels put the Dutch oven on your stove top, and remove the cover. Using the parchment, lift the dough out of the bowl and rest it (along with the parchment paper) in the Dutch oven. Cover the Dutch oven (remember it's hot!) and return it to the stove.
Bake for 20 minutes. Remove the lid and bake for another 30 minutes or so (if you want to be sure it's done, an instant read thermometer should read about 205˚F). Remove it from the rack. Resist cutting into it for at least one hour! This is much harder than it sounds.