In a large mixing bowl, combine the fed starter, warm water, and 3 cups of all-purpose flour. Stir vigorously with wooden spoon until combined, approximately 1 minute. Cover with plastic wrap and let rest at room temperature for 1 hour. Refrigerate overnight.
Mix the Bread Dough
The next day, remove the levain from the refrigerator and allow to come to room temperature, about an hour.
In a large mixing bowl, with kneading hook attachment, combine the levain with the remaining 2 cups all-purpose flour, granulated sugar, and kosher salt. Begin mixing at a low speed, adding up to 1/4 cup water as needed to make a smooth dough. Continue kneading for 5-7 minutes.
Transfer dough to a large greased bowl and cover with plastic wrap. Allow the dough to rise until it has doubled. (This may take 2-3 hours). (Remove the dough at each hour interval to stretch and fold the dough on a smooth surface, envelope-style to work the gluten in the dough. The dough will most likely be sticky, but refrain from using flour. Instead, use a stainless bench scraper to lift the dough from the work space.)
Form Dough into Loaves
Once the dough has doubled, divide the dough in half. Stretch and fold the dough, envelope-style, again using the bench scraper as needed. Form each into a ball. Cover and allow the dough to rest for 30 minutes.
Flatten each ball into an rectangle. Stretch and then fold the dough, envelope-style. Form a nice smooth ball, pinching on the bottom. Slide the bottom of the dough against your work surface to seal the seam.
At this point, you may either place the dough into a Dough Banneton Basket that has been sprinkled with Brown Rice Flour or place it on a greased sheet of parchment paper or bread sling. Cover and allow to rise for 1-3 hours until puffy. Halfway through the rising time, preheat oven to 475F degrees.
Score and Bake the Bread
Uncover the risen dough. If using the Banneton, turn dough out onto a bread sling or sheet of parchment paper. Using a knife or bread lame, slice or or two fairly deep horizontal slashes in each.
Holding opposite sides of the sling or parchment paper, lift the dough and place in a 4-6 quart Dutch Oven. Spritz with water (2-3 times) to help create steam in the oven.
Cover with lid and bake in preheated oven for 20 minutes.
After this initial baking period, uncover each Dutch oven and reduce the oven temperature to 450F. Continue baking for an additional 12-14 minutes until golden brown. To prevent your loaves from burning on the bottom, place a baking sheet beneath the Dutch Ovens on a lower rack.
If time allows, you may cure your bread by turning off your oven and cracking open the oven door for 20 minutes. This will give your bread a crackly, crunchy crust.
Transfer bread from Dutch Ovens to wire racks to cool completely. Makes 2 loaves of bread.