Activate the preferment (4-5 hours)
In a medium bowl, whisk 2 TB sourdough starter into 100ml water until combined. Add 100g flour and mix just until you have a thick, craggy dough with no dry flour. Cover and rest in a warm place until mixture has doubled and looks thick and bubbly. (4-5 hours) If the mixture hasn’t roughly doubled at this point, add a little more flour and water and allow to ferment for some additional time. 

Make the dough/autolyse (~30 mins)
In a large bowl, combine the preferment with 400ml water and 500g of bread flour, 50g of whole wheat flour, and 50g spelt flour (or whatever flours you are using). Mix just until all the flour has been hydrated (using another splash or two of water, if needed). Cover with plastic and let rest 30 minutes. (30 mins)

Stretch & fold + bulk fermentation (~4 hours)
1. Uncover the bowl, sprinkle 2 tsp sea salt and a splash of water on top, and work in with hands until integrated.

2. Either in the bowl, or on an oiled counter, begin to stretch-and-fold the dough for a few minutes, until it begins to feel elastic and a little “bouncy.” Use a silicone dough scraper to help scoop the sides of the dough up as you work. This is messy work; expect the dough to remain sticky, though it will become more elastic and firm as you go.

3. Return the dough to the bowl, cover, and rest at room temperature for 30 minutes. Then remove plastic, pull and stretch the dough in the bowl 4-5 times, then re-cover and let rest in a warm spot for 4 hours. (note: if your dough does not seem very elastic, you can repeat the stretch-and-fold process two more times, with a thirty-minute rest in between each. If the dough becomes difficult to stretch and doesn’t want to bounce back, let it rest). You’ll know the dough is properly fermented when it has grown by about 30 percent, has a few nice big bubbles on the surface, and a slightly shiny appearance. 

Shape the dough (40 mins)
1. Prepare your final proofing container: either a banneton basket or a medium bowl lined with a clean kitchen towel and sprinkled very liberally with flour. 

2. Pre-shape: Turn the dough onto a floured surface (sticky side up), then gently pull and stretch the dough from the bottom to the middle to create a ball shape, pinching the ends together in the middle to seal them together. If you prefer a batard or oblong shape, form the dough into a rough rectangle and fold one end halfway up the rectangle, then fold the other end in to meet it. Roll the dough into a rough log, using your fingertips to pinch together a seam along the length of the loaf and tuck and to seal the ends. 

Be careful to do this process gently so as not to deflate the gases that have allowed the dough to rise. Flip the dough over, cover with a tea towel, and rest for 30 mins. 

3. Final shape: Using the knife edge of your hands or a silicone dough scraper, slowly and carefully tuck the sides of the ball/batard under on all sides to create additional surface tension on the top of the loaf, again being careful not to deflate the dough. Carefully transfer the dough ball to the banneton or towel-lined bowl, placing it seam-side up. Cover with plastic or a tea towel. 

Final proof (2-12 hours)
If baking immediately, allow the dough to prove at room temperature for two hours, or until it slowly springs back when poked. If time allows, I strongly recommend allowing a longer proof in the fridge for 8-12 hours. This allows the gluten to develop further and results in much better flavor. 

Final prep and baking (2 hours)

1. Place a dutch oven (or pizza stone, if no dutch oven is available) inside your oven and preheat at 475-500 degrees (the hotter, the better) for 30 mins – 1 hour. Tip: place the dutch oven on top of a baking sheet to help prevent a burned bottom crust.

2. If dough has proved overnight in the fridge, remove and allow to rest at room temperature while the oven is heating. Test the dough: You’ll know it’s ready to bake when you poke the dough gently with your finger and it springs back slowly (if it springs back very quickly, it needs a few more minutes; if the indentation stays, it has over-proved and should be baked immediately). 

3. Turn the dough onto a piece of parchment paper, seam side down. Using a very sharp knife or razor blade, quickly and carefully score the bread, either two end-to-end criss-cross cuts, or some other decorative pattern. The key is to allow the bread a way to expand while baking so it doesn’t split.

4. Remove the hot dutch oven from the oven and carefully transfer the dough, still on its parchment, into the pot (or transfer to baking stone/sheet, if using). Spritz or sprinkle the dough with water (to help create steam for a crisp, crackly crust), then replace the dutch oven lid, return to oven, and bake, covered, for 25 minutes. 

5. If using a dutch oven, reduce oven temperature to 450 degrees, remove lid, and bake 25-30 minutes more, until loaf is deep brown. (If baking on a stone or sheet, continue to bake uncovered until the crust is deep and dark.) 

Cool on a baking rack, avoiding slicing until the loaf is thoroughly cooled, about an hour. The loaf can be left out at room temperature for one day; after that, wrap it in plastic and place inside a zippered plastic bag.