Sourdough starter - I use a 50/50 mix of Shipton Mill Untreated Organic White Flour - No.4 (105) and a dark rye flour and mix that with the same weight of water. I referesh it a couple of times the day before I bake, otherwise it lives in the fridge. The quantities given below rely on using this Shipton Mill flour, when I use different flours the amount of water changes.
625g filtered water, warmed (this can be increased to 650g depending on the weather)
16g salt (I use wet grey french rock salt ground fine)
50g dark rye
950g strong white flour
Mix all the ingredients and french fold them until the dough is no longer sticky and you don't get any tears on the surface meaning the gluten is sufficiently developed. This should take less than five minutes and folds air into the dough rather than kneading the air out of it.
Prove sealed in a plastic food box for three to four hours. If it's cold then put a baking tray under the box and keep it topped up with hottish water.
Divide and fold into preferred loaf shape, leave seal down (so the loaf is top side up) for 15 minutes, then fold again finally stretching to surface until just before it starts to tear - but do not let it tear. Knowing this moment takes a bit of experience.
Place seal up (so the loaf is top side down) in a banetton that has been generously floured with rice flour and put in a sealed plastic box until risen to a bit less than double in size. If you prod the loaf (gently) with your fing it should recover slowly. If it springs back it is not yet ready, if the indentation remains get it in the oven fast! This will take a couple of hours.
Preheat the oven to 220-250 degrees C. This means you want it to have reached temperature about 30 minutes before the loaves go in to make sure all the oven is fully up to temp, particularly if you have granite stones in your oven. These take a long time to heat up and are not measured by the oven thermometer. Unless I am filling the oven with bread (in which case a fair amount of steam comes out of the dough anyway) I put a baking tray full of water onto one shelf to keep the air really moist.
I do not put my loaves directly on my granite stone due to the complaints about the state I leave the oven in, so I put a silicone sheet in a shallow baking tray, heavily dust it with semolina then turn out the loaves onto all this. Slash them deep and fast with a very sharp knife or lame (I use a chinese knife that is soft and easy to put a razor sharp edge on, I just don't get on with razors). Put the tray in the oven, spray the sides of the oven (not the loaves) with water (I use a plant spray) and get the door closed as quickly as possible. I spray again every two to three minutes for the first 10 to 15 minutes. Bake for 30 minutes (obviously depends on the size of your loaves, I usually bake a mix of 480g boules and 700g batards). When a good colour is attained get a loaf out and use a probe thermometer to check the inside temperature - you are looking for 90 degrees C. As soon as you have that temperature (and the crust colour you want) get the loaves out and onto a cooling rack.
If you freeze the excess loaves then, after thawing, put them in a 200 degree C oven for five minutes to get the crust back.
Doing it this way makes sourdough no more fussy than yeasted bread, they just take a little longer.