Feed your sourdough starter 4-12 hours beforehand until it becomes active and bubbly.
Mix warm water and flour in a large bowl. Let this mixture rest for 30 minutes to allow the flour to fully hydrate.
Using wet hands, incorporate the sourdough starter into the flour mixture. Sprinkle salt on top.
Using your hands, combine the dough for approximately 5 minutes until it comes together. Cover and rest for 30 minutes.
Perform 6 rounds of stretch and folds: first 3 rounds every 15 minutes, last 3 rounds every 30 minutes.
Cover dough and allow to bulk ferment until doubled in size. Look for small bubbles on the surface.
Divide dough into three equal portions. Create tension and form each piece into a ball. Rest for 20 minutes.
Stretch each piece into a 10x5 inch rectangle. Fold long sides to center, seal seam, then roll seam-side down. Create tension by pulling against counter to elongate to 14 inches.
Place shaped baguettes in baguette mold or baker's couche. Cover and refrigerate overnight or up to 36 hours.
Preheat oven to 500°F with baking stone for 1 hour. Place cast iron skillet on bottom rack. Prepare boiling water.
Remove baguettes from fridge. Score tops with 3-4 deep cuts at 45-degree angle. Fill skillet with boiling water for steam.
Spritz baguettes with water. Place on baking stone, reduce heat to 450°F, and bake for 35 minutes, rotating at 20 minutes for even browning.