Activate Starter (8 hours)

• Discard all but 3 tablespoons (50g) of starter. You can use discarded starter for other purposes.
• Mix in 50 grams of 78°F/26°C water and 50 grams all-purpose flour.
• Mix thoroughly until there aren’t any dry bits of flour.
• Cover mixture with a towel or paper towel and let it rise overnight or about 6 to 8 hours.

Mix Dough (40 minutes)

• In a large heavy bowl, mix 350 grams of 80°F/27°C water and 100 grams of active starter.
• Add the flours and mix thoroughly with spatula or dough whisk, making a "shaggy" dough. Ensure there aren’t any dry bits of flour.
• Cover bowl with dish towel and let the dough rest for 25 to 40 minutes.
• At the end of the resting period, dough should look less shaggy and smoother.
• Add 10 grams salt and 25 grams of 80°F/27°C water. Use your hands to mix it and make sure the salt is worked through all of it. Once the water and salt are mixed in and the dough feels more cohesive, do one or two turns.
• To do one turn, take the side of the dough furthest away ("12:00" of the bowl), and gently lift it out of the bowl until it stretches, then fold it back on itself towards you ("6:00" of the bowl). Wait 10 seconds. Turn the bowl one-third (about 120 degrees) and repeat the lift and fold. Wait 10 seconds, turn bowl one-third and repeat lifting and folding. This is one turn.

Bulk Fermentation (4 hours)

• This is the first rise for your bread, and it will take 3 to 4 hours if your kitchen is relatively warm (78-82°F/25-28°C). In a cooler kitchen, it will take at least 4 hours, maybe longer. Leave the dough in its bowl and cover it with a kitchen towel.
• Every 30 minutes, do one gentle turn of the bread. During the bulk fermentation, you want your dough to aerate, so don’t knead or push all the bubbles out as you turn.
• Dough will increase in volume noticeably after a few hours. (A good rule of thumb is you want it to roughly double in size.)

Pre-shape Dough

• Flour your work surface and use a spatula to pour the dough out onto the floured surface. A tea ball works very well for dusting flour.
• Fold the dough back onto itself, and flip it over so the seam is down.
• Tuck the bottom under to shape it into a ball, building tension in the outer layer as you shape it. Use your bench scraper or your hands to tuck the dough under into itself as you go "around" the ball.
• Sprinkle the top of the dough lightly with flour and cover with a kitchen towel.

Bench rest and Final shaping (30 minutes)

• Let dough rest on your work surface for 20-30 minutes. It will relax into a fat pancake shape.
• If it looks too runny, do a second shaping and a second bench rest to develop tension in the surface.
• Flip the dough over so the seam is up.
• Gently stretch the dough out so that it resembles a thick pizza crust (about 12 inches round). Do not tear or overwork dough! Then, pick one side with your thumb and forefinger, stretch it away from the center of dough, and fold it back into the center. Repeat with the opposite side. Repeat, going around the dough until you have created a dumpling-like shape, while creating tension on the bottom (which is the top of the loaf).

  Pinch the seams together until they form a smooth(er) ball. Flour the top (which is the bottom of the dough).
• Let your dough rest for a minute.
• If you use a proofing basket/banneton, flour the inside generously so dough doesn’t stick. If you use a bowl, line the inside with a kitchen towel and then flour the towel generously.
• Gently pick up your dough and set it into the basket/bowl. The seam side should be facing up.
• Flour the seam.

Final Rise/Proofing

Same Day (2-4 hours)

• Let the dough rise in your kitchen for 2-4 hours (if your kitchen is relatively warm (78-82°F/25-28°C); if it's cooler than that, extend the time. The shorter the final rise time, the milder your loaf will taste. The longer, the more sour it will taste.

Overnight Slow Proof (8-16 hours)

• You can extend the final rise by putting your dough in the fridge overnight for 8-16 hours. (This is also handy to let the sour flavor develop, and it lets you bake fresh bread first thing in the morning!)

Bake (1 hour)

• Place a heavy covered dutch oven or bread baker in the oven and preheat to 500°F/260°C.
• Remove bowl with dough from fridge if you did an overnight rise (no need to let it come to room temp first).
• Gently invert it onto a piece of parchment paper so the seam side is down.
• Once oven is hot, carefully slide the rack out and uncover the dutch oven.
• Dust the bottom of the dutch oven or bread baker with flour (not needed if using parchment).
• Score the top of the dough with a serrated knife or bread lame.
• Carefully place the dough into the hot oven.
• Cover the dutch oven and slide it back in the oven.
• Turn the oven temperature down to 450°F/232°C.
• Bake covered for 20 minutes.
• Remove the lid from the dutch oven/bread baker and bake for an additional 18 to 22 minutes until the loaf is golden brown. To test for doneness, thump the bottom of the loaf. If it sounds hollow all the way through, it is done. If it feels "wet" or solid, bake a few more minutes and check again.
• Remove bread from oven and dutch oven, and let cool on baking rack at least 90 minutes.
• Consume within 2 days, or slice, then store in airtight bag and freeze bread.