On Day 1, mix the whole wheat flour and cool water in a clean glass mason jar.

Cover the jar loosely and leave it on your countertop for 24 hours.

On Day 2, discard half of the mixture from the jar.

Add ½ cup of water to the remaining starter and stir to thin it out.

Mix in 1 cup of unbleached all-purpose flour, cover loosely, and wait 24 hours.

On Day 3, begin feeding the starter every 12 hours (twice a day) using the same ratio: discard half, add ½ cup water, and add 1 cup of unbleached all-purpose flour.

Continue this twice-a-day feeding schedule until your starter begins to bubble vigorously and doubles in size, which typically takes about 7 days.

Once your starter is active and bubbly, measure out 200 grams into a large mixing bowl.

Add the bread flour, water, and salt to the bowl.

Mix everything together until a shaggy dough forms.

Cover the bowl with a clean kitchen towel and let the dough rise until doubled in size.

Preheat your oven to 450°F and place a heavy Dutch oven inside to heat up.

Carefully transfer the risen dough into the hot Dutch oven lined with parchment paper, or place it in a loaf pan rubbed with olive oil.

Cover the Dutch oven with its lid and bake for 30 minutes.

Remove the lid and bake uncovered for a final 15 minutes until the crust is dark, blistered, and caramelized.

Allow the bread to cool completely before slicing.