Mix 230 grams of ripe levain (you will have some leftover), room temperature water, flour and salt in a bowl using a wooden spoon or dough whisk (affiliate link). The dough will look “shaggy” but will come together. Cover the bowl and let it sit for an hour. After an hour, uncover the bowl and do a series of three "stretch and folds". To do this, pick up the underside of the dough and fold it on top of itself, turning the bowl after each fold and picking up a different section of the dough to fold and turn. An example of this folding technique is found here (halfway through the video).
Cover the bowl again and let it rest for another hour. Notice how the dough is coming together. It doesn’t feel shaggy anymore and is becoming more stretchy and cohesive. For the second time, do the series of three stretch and folds.
Cover the bowl again and let it rest for its third and final hour. Repeat the series of three stretch and folds.
Let the dough rest for it's final hour. At this point, the dough should have risen 30-40%, have some scattered bubbles over the top of the dough, pull away from the sides and start to dome toward the center and feel more elastic. If it doesn't look that way, let it keep fermenting for another 30 minutes and check again. Check your dough temperature and make sure your dough is in the 78 degree F range.
Cover the bowl with plastic wrap or a lid and put it in the refrigerator to rest overnight. The dough can stay in the refrigerator for 8 to 48 hours. See recipe notes for instructions on baking the same day.
The next morning (or whenever you are ready to bake your bread), put a dutch oven (affiliate link and see recipe notes for more options) into your oven with the lid on and set the oven to 500 degrees. Preheat the dutch oven by leaving it in the oven for 30 minutes.
Immediately after setting the dutch oven to preheat, pull out a piece of parchment paper. Take your dough out of the fridge and shape into a round ball. Do not punch down the dough, just lightly form with the palms of your hands. It should be fairly easy to work with because it is cold.
When your dutch oven has preheated for 30 minutes, score the top of your bread with a bread lame (affiliate link), sharp knife or razor.
Take the dutch oven out of the oven. Warning: This is a VERY HOT dutch oven. Keep those oven mitts on and be very careful not to burn yourself. Take the top off the dutch oven and place the dough and parchment paper into the dutch oven. Place the top back on the dutch oven and close the oven door.
Immediately decrease the baking temperature to 450 degrees and bake for 25 minutes.
After 25 minutes, take the top off the dutch oven and continue baking for 20 more minutes. This will produce the crisp crust you are looking for.
Pull your bread out of the oven. Wait (if you can) to cut into it until your bread has cooled. Enjoy!