aka levain, preferment, sponge, poolish, or biga
This makes 80g of leaven, with a little left over for the next time. You may want to scale down as low as 60 for very warm climates or if you want to slow things down. In the winter, I usually go up to 100g.
8 - 24 hours. Longer will be more sour.
Add in salt, mix thoroughly.Stretch & fold 4 or 5 times, waiting at least 20 minutes between each. This counts as part of the bulk fermenation phase.
The total amount of flour is consistent, although you can play with the proportions and types. White flour makes for loftier bread, whole grain flour gives more flavor.
Wetter dough is harder to work with, but gives a more open crumb (think ciabatta). Try 350g water for something easier to work with, or bump up to 400g, particularly with more whole grain flour.
Dust the top of the dough with a little flour. Flip over and gently stretch out. Fold the bottom third up, then the right third, left, and finally top. Roll over so the seam is down. Slide across countertop with hands and/or bench knife to build tension.
Dust banneton and dough with rice flour. Put dough in banneton with the seam-side up. Dust that side with more rice flour and cover with a towel.
Put the lid on the pan, return to oven and bake 25 minutes.
Reduce the heat to 450°. Remove the lid from the pan and cook until the bread is nice and dark. 10-20 minutes.