Begin by combining the bread flour and water in a bowl, mixing until well incorporated. Cover and let it rest for 30 minutes to 2 hours.

After the resting period, introduce the sourdough starter by pressing it into the dough. Dampen your hand to prevent sticking. Cover and let sit for another 30 minutes.

Sprinkle kosher salt over the dough and mix it in evenly. Cover and let rest for another 30 minutes.

Perform a series of stretch and folds: pull one portion of the dough up and fold it over itself, rotate and repeat until you’ve gone around the dough. Rest for another 30 minutes. Repeat for a second stretch and fold.

Spritz the work surface with water, then turn out the dough. Flatten it into a rectangle, sprinkle with most of the onion powder and oregano, add the cheddar and jalapeños, then fold the dough over to enclose the fillings. Rest for another 30 minutes.

Start the coil folding process by tucking the dough under each side. Repeat this twice at 30-minute intervals.

Allow the dough to bulk ferment until it expands by at least 50% to nearly double in size (5-6 hours).

Prepare your banneton by dusting it with rice flour. Turn the dough onto a floured surface, shape it and place it seam side up in the banneton, covering it and refrigerating overnight.

Preheat your oven to 475°F with a Dutch oven inside. Remove the dough from the fridge, flip onto parchment, score the top, and transfer to the Dutch oven covered.

Bake for 20 minutes, reduce temperature to 450°F, remove lid and bake for another 10 minutes, then reduce to 425°F and bake for 10 minutes more.

Cool on a wire rack for at least three hours before slicing.