Add the water and starter to a large mixing bowl and whisk to combine.
300 grams water, 100 grams active sourdough starter
Add the flour and salt to the bowl, and use a wooden spoon or spatula to mix until a shaggy dough forms. Finish mixing with your hands to fully incorporate the flour.
550 grams spelt flour, 10 grams fine sea salt
Cover the bowl and set aside to rest for 30 minutes.
Once the dough has rested, begin your stretches and folds. Do three rounds of stretches and folds over the course of an hour, once every 20 minutes.
Form the dough into a ball or boule by placing it onto a clean surface and using your hands to rotate until surface tension forms.
Line a proving basket with a tea towel and sprinkle with flour. Place the dough upside-down into the prepared basket.
Cover and set aside to rise at room temperature for three hours. The dough should visibly rise during this time.
Place the dough into the refrigerator overnight, or for at least eight hours.
Place a heat-safe dutch oven into the centre rack of your oven and preheat the oven to 240°C (465°F).
Turn the dough out onto a piece of parchment paper and score with a sharp knife.
Carefully remove the dutch oven and place your loaf into it, using the parchment paper as handles to lift the bread.
Bake for 20 minutes with the lid on, then remove the lid and reduce the temperature to 220°F (425°F) and bake for another 15-20 minutes, or until browned to your desired degree.
Remove from the oven and cool in the pot for ten minutes before carefully removing the bread and cooling fully on a wire rack. It must be completely cool before slicing.
I recommend storing it in the pot you've baked it in, or freezing individual slices and toasting to thaw.
Video
Notes
Note that the dough will be quite stiff immediately after mixing. You'll probably need to stretch with both hands for the first round of stretches and folds, and then as the gluten relaxes, the following rounds will be easier and more like white flour bread. See video for a visual of this.Update 01/23: I tried doing the cold method for this bread (not preheating the pot in the oven) and it's okay, but not nearly as good. If you want to try this, bake the bread for 30 minutes with the lid on before removing and baking until brown, but I'd recommend just making a pan loaf instead.