• Activate starter. Combine 30 grams of sourdough starter, 70 grams of all-purpose flour, 30 grams of rye flour (optional, you can replace the rye flour with all-purpose flour), and 100 grams of warm filtered water. Stir to combine and allow to sit until it’s doubled in size and is nice and bubbly.

Make Dough

• Mix the starter and water. In a large mixing bowl, add the sourdough starter and warm water. Stir to combine using a spatula, whisk, or Dutch bread whisk.
  
• Add half the flour. Add half of the flour to the bowl and stir to combine. This will be a very wet mixture but you want to make sure the flour is fully incorporated.
  
• Add flour and salt. Add the rest of the flour and the salt. Stir to combine.
  
• Rest. Cover with a tea towel and allow the dough to rest for 30 minutes.

Stretch and Folds

• First stretch and fold. After 30 minutes, start the process of stretch and folds. Start from one edge of the bowl and stretch the dough up and towards the middle, folding the dough over itself. Turn the bowl ¼ turn and repeat until all of the dough has been stretched and folded towards the middle.
  
• Repeat. Cover the dough again with a towel. Wait 30 minutes and repeat. (You’ll want to do 3-5 series until the gluten is well developed. You will know it is done when the dough looks smooth and soft and you can stretch the dough without it breaking or ripping.)
  

Bulk Rise

• Rise. Allow the dough to sit covered, and undisturbed for 4-6 hours in a warm dark place.
  
• Cold Ferment. Transfer the dough to the refrigerator to cold ferment for 8-12 hours.

Shaping

• Prep. Line a baking sheet with a piece of parchment paper and set aside. Remove the dough from the refrigerator and turn out onto a clean dry surface.
• Divide dough. Separate the dough into 6 equal pieces.
• Shape. Shape them into balls and transfer them to the prepared baking sheet.
  
• Score. Use a bread razor (or really sharp knife) to score the dough balls with an X on top.
• Rise. Cover and allow them to come to temperature and rise for 1 hour.

Baking

• Prep. Arrange the racks in your oven so you have a rack in the lower 3rd of the oven and 1 rack in the center of the oven. Place a baking stone in the oven on the center rack. Preheat the oven to 450°F and allow it to warm for 30 minutes.
• Add ice. Fill a baking sheet with about 1 cup of ice. Add the baking sheet with ice to the bottom rack of the oven.
• Bake. Transfer the dough balls to the baking stone and bake for 25-30 minutes or until golden brown.