Build the levain in the morning. In a jar add the water, starter and flour and mix well. Place in a warm spot until it rises to its peak level (4-6h, depending on your starter's schedule).
When your levain is at peak, start building the dough. In a mixing bowl add the water, then the levain and stir a bit until the levain dissolves. Add the flours and with your hand or with a spatula mix everything together until all the flour is wet. Make sure there are no pockets of dry flour left. Cover and let rest in a warm place for 30 minutes (fermentolyse).
Add the salt and dimple into the dough with your wet fingers. Fold the edges to cover the salt, then squeeze and start working the dough so the salt distributes well. I use a mix of Rubaud kneading method and a one handed slap and fold directly into the bowl, for about 2 minutes. Cover and let rest for 30 minutes more.
Perform a strong stretch & fold. Cover and let rest another half an hour in a warm place.
Perform 3 coil folds separated by 30 minutes. Handle the dough as gentle as possible towards the end, as it's becoming more airy. If you feel it is already strong enough and holding its shape, perform only half a fold. Listen to the dough.
After the last coil fold let the dough finish bulk fermentation in a warm place, untouched. For mine it usually takes about one hour more. But look at the dough rather than at the time. You are looking for visible signs of rising (30-50% rise) and fermentation bubbles on top and on the side if using a transparent bowl like I do.
Transfer the dough on your clean working surface. Use your bench knife to preshape the dough, the let bench rest 15-20 minutes. If the dough is already very proofy, cut the rest short at 15 minutes. If you feel it would need some extra fermentation, you can let it rest for up to 30 minutes or so.
Lightly dust the preshaped dough and your working surface. Use your dough scraper to turn the preshaped dough upside down on the floured surface. Gently shape your dough in your desired way - boule or batard. Let rest on an unfloured surface for a couple minutes, so it sticks back together.
Meanwhile lightly dust the banneton. Then gently place the shaped dough in it and stitch if you feel the dough needs a little extra tension. Cover and place in the fridge for cold fermentation overnight (4-6C for 12-20h)