10:00 PM – Levain and Poolish Launch: Prepare two separate small glass jars or containers. For the Levain: Whisk 5g of starter culture into 35g of room-temperature water, then stir in 30g of all-purpose flour and 5g of rye flour. For the Poolish: Dissolve 0.5g of dry instant yeast into 100g of water, then stir in 100g of flour until a smooth, thick batter forms. Cover both vessels loosely and let them ferment concurrently side-by-side at a room temperature of 70–75°F (21–24°C) overnight for 10 to 12 hours. By morning, both preferments must look aggressively bubbly, frothy, and expanded to their absolute peak.

10:30 AM – First Fold Interval: Let the dough rest inside the covered bin for 30 minutes at a warm room temperature of 74–78°F (23–26°C). Wet your hands thoroughly with water to prevent sticking. Slide your hands beneath the wet dough, pull it upward gently from the center to stretch it without ripping, and fold it over onto itself. Repeat this action on all four quadrants of the dough. Close the lid.

Progressive Folds: Continue building vertical vertical strength and organizing the large gas pockets by executing three more rounds of regular stretch-and-folds inside the bin spaced exactly 30 minutes apart: - 11:00 AM – 2nd stretch and fold. - 11:30 AM – 3rd stretch and fold. - 12:00 PM – 4th/final stretch and fold.

The Cold Fermentation Retard: Following the final fold, leave the dough undisturbed for 15 minutes. Look for a distinct lightness, a 50% increase in total volume, and prominent surface bubbles. Transfer the closed container directly into the refrigerator to undergo an overnight cold fermentation retard for 11 to 24 hours.

The Next Day – Flipping the Wet Matrix: Remove the cold, structured container from the refrigerator. Generously dust your work table and the top surface of the cold dough with a heavy layer of flour. Invert the container smoothly onto the counter, allowing the cold dough to slide out naturally under its own weight without pulling or stretching it forcefully.

The Clean Scraper Divide: Using a large bench scraper dusted with flour, split the rectangular dough sheet cleanly down the middle into two equal parts. For a more voluminous shape, take each piece and fold the wet, sticky, flourless cut sides inward facing each other. Dust with additional flour around the edges.

The Linen Couche Rest: Transfer each shaped loaf carefully onto a well-floured proofing couche or a heavy kitchen cloth, pulling the fabric upward between the loaves to create a supportive wall that forces them to rise vertically rather than flattening out. Cover loosely with a towel and let proof at room temperature for 1 hour to 1 hour and 30 minutes. Perform a poke test—if your finger leaves an indentation that slowly springs halfway back, it is ready to bake.

Preheating and Setup: One hour before baking, place your baking stone on the middle rack and an empty metal iron tray on the bottom rack, preheating the oven to a smoking hot 500°F (260°C).

The Inverted Bake: Flip the proofed ciabattas over carefully onto a sheet of parchment paper so that the sticky bottom side now faces directly upward. Prepare 10 solid ice cubes. Act quickly: slide the loaves along with the parchment paper onto the scorching hot baking stone, dump the ice cubes straight into the bottom iron tray to release a massive plume of steam, and slam the oven door shut. Bake with steam at 500°F (260°C) for exactly 10 minutes.

The Crisp Uncovered Finish: Carefully open the oven door to vent any remaining steam, remove the bottom water tray, lower the temperature down to 475°F (246°C), and continue baking uncovered for an additional 15 minutes until the crust turns an even, crisp, light golden-amber finish. Transfer to a wire rack and let cool completely before slicing.