Place 600 grams all purpose flour, 1 tablespoon vital wheat gluten, and 12 grams of Kosher salt in a large mixing bowl. Stir to combine.
Add 400 grams water, and the ripe Levain to the dry ingredients in the mixing bowl. Stir together with a Dutch dough whisk until you have a lumpy, shaggy, dough and the dry ingredients have been incorporated into the dough.
Cover the bowl with plastic wrap and allow dough to rest for 1 hour.
FIRST STRETCH & FOLD: After one hour, wet hands. Stretch and fold dough 4-5 times, turning bowl a quarter turn after each stretch and fold.
Cover bowl with plastic wrap and allow dough to rest for 1 hour.
SECOND STRETCH & FOLD: After one hour, wet hands. Stretch and fold dough 4-5 times, turning bowl a quarter turn after each stretch and fold.
Cover bowl with plastic wrap and allow dough to rest for 1 hour.
THIRD STRETCH & FOLD: After one hour, wet hands. Stretch and fold dough 4-5 times, turning bowl a quarter turn after each stretch and fold.
Cover bowl with plastic wrap and allow dough to rest for 1-2 hours until dough puffs in the center and pulls away from the sides. Try to maintain temperature at 78-80℉. When bulk fermentation is complete, the surface should have some visible bubbles that have formed. Keep checking dough every 30 minutes until dough has completed the bulk fermentation process.
Place covered bowl in the refrigerator overnight. Dough will cold ferment and sourdough flavor will intensify during cold fermentation. Dough can be left in the refrigerator for 12 to 48 hours.
When ready to bake, remove dough from the refrigerator. Place a Dutch oven pot in the oven and preheat oven to 500 ℉.
Lightly flour work surface and remove dough from the bowl. Use your hands to shape the dough into a round boule pulling the dough out and down, stretching the dough to help develop the gluten strands.
Dust the top of the loaf with flour and transfer dough onto a sheet of parchment paper. Cover with bowl and allow the dough to rest as the Dutch oven pot preheats in the oven for 30-45 minutes.
Using oven mitts, carefully remove the hot Dutch oven pot from the oven.
Score loaf with a sharp knife.
Use the four corners of the parchment paper to lower the dough into the Hot Dutch oven pot, being careful not to burn yourself.
Place lid on the pot and return it to the oven.
Immediately lower oven temperature to 450℉ and bake loaf for 25 minutes.
After 25 minutes, remove the lid and continue to bake uncovered for another 20 minutes.
Remove from oven and lift loaf out of the pot. Place loaf on a cooling rack and allow loaf to cool completely before slicing into it.