Sourdough Loaf

Ingredients

Around lunchtime, pour the sourdough starter into a mixing bowl. (I generally start with about 1½ cups of starter in my jar, so when I pour off the amount I need, there is ½ cup or so left in the jar, which I will feed for future loaves.)
Add the warm water and gently stir with a fork or your fingers to dissolve the starter into the water.
Add all three flours and stir well, until no dry flour remains in the bowl. Cover the bowl with a clean, dry kitchen towel and allow the dough to rest for about 1 hour.
After the resting period, sprinkle the salt over the top of the dough in the bowl. Sprinkle about 1 tablespoon of water over the salt. Fold the salt into the dough, replace the kitchen towel, and set the bowl in a warm place: 68°F to 70°F is ideal for the timing specified in this recipe; if your home is much cooler or warmer, your dough will take a longer or shorter period to rise.

The dough will take 4 to 6 hours to ferment and rise. For the first 2 hours, fold and turn the dough every 30 minutes, three or four times total. The dough is fully risen when it is smooth and bubbly and roughly double in size. (I highly recommend using the same bowl for each batch of dough: you'll learn exactly what level the dough should rise to for the ideal texture.)

In the evening, tip out the fully risen dough onto a floured work surface. Using a bench scraper or large knife, divide the dough in half. Gently shape each dough into a loose ball with your hands.
Prepare two proofing baskets or two medium-size mixing bowls with kitchen towels by dusting them generously with flour. Set aside.
To shape the loaves, first sprinkle a pinch of flour on top of one ball of dough. Turn the ball over so the floured top is on your work surface. Pull up the outside edges of the dough and tuck them into the middle to form a tighter, smoother ball. Flip the ball over so the seam side is on the work surface. Now use your hands to drag the dough a small distance across the work surface toward yourself, then rotate in a quarter turn and drag again. Rotate and drag once or twice more to increase the tension of the shaped dough and seal the seam on the bottom. Repeat with the other dough ball.

Dust the top of the shaped dough with a pinch more flour, and place each ball seam-side-up in a floured proofing basket. Cover with the kitchen towel you used to cover your dough bowl, and set the baskets in the refrigerator. Allow the loaves to rise slowly in the fridge overnight.

In the morning, place your two Dutch ovens in the oven and heat to 500°F. Tear off two roughly square pieces of parchment paper.
Take your dough out of the refrigerator. Hold a piece of parchment paper over a dough ball, then carefully turn over the basket to release the dough, upside-down, onto the parchment. Using a lame, razor blade or sharp knife, score the dough with shallow cuts so the loaf will rise evenly and successfully in the oven: I recommend cutting an X across the center, at four long parallel slashes. (You may eventually like to experiment with alternative scoring designs and techniques as well.) Repeat with the second dough ball.
Take the lids off the preheated Dutch ovens and place the scored loaves inside, parchment paper and all. Replace the lids and bake for 20 minutes. Lower the oven temperature to 450°F and bake for another 10 minutes. Finally, remove the lids and bake for about 20 minutes more, until the crusts are golden brown. and the bottoms of the loaves sound hollow when tapped.
For the best texture, let the bread cool at least an hour (preferably 2 hours) before slicing.