01 - Combine bread flour, whole wheat flour, and water in a large mixing bowl. Mix until just incorporated with no dry patches. Cover the bowl and let rest for 1 hour to hydrate the flour.
02 - Add the active sourdough starter and sea salt to the rested dough. Mix thoroughly by hand or using a spatula until the starter is fully distributed and salt dissolves throughout the dough.
03 - Cover the bowl and allow the dough to ferment at room temperature for 4 to 5 hours. Perform stretch and folds every 30 to 45 minutes, completing 4 sets total to develop gluten strength.
04 - Turn the dough onto a lightly floured work surface. Gently shape into a round ball without degassing. Cover with a towel and let rest for 20 minutes to relax the gluten.
05 - Shape the dough into a tight round loaf, creating surface tension. Place the loaf seam-side up in a well-floured proofing basket or lined bowl.
06 - Cover and proof at room temperature for 2 to 3 hours until increased by 50 percent. For enhanced sour flavor, refrigerate overnight for 12 to 16 hours.
07 - Position a Dutch oven or heavy cast-iron pot with lid in the oven. Preheat to 480°F for at least 30 minutes to ensure proper heat retention.
08 - Gently invert the dough onto parchment paper. Score the surface with a sharp blade or lame. Transfer to the preheated pot, cover with lid, and bake for 20 minutes. Remove lid, reduce temperature to 430°F, and bake 25 minutes until deep golden brown.
09 - Remove the bread from the pot and transfer to a wire rack. Cool completely for at least 2 hours before slicing to allow the crumb to set properly.