Sourdough starter instructions here.
(Keep in mind that I built an earth oven for baking bread, so I tend to go a little overboard on these things. But bread is for me a delightful thing, something that is nourishing physically and aesthetically.)
Sourdough requires a sponge---basically the dough for the rest of the dough.
Take your starter from the fridge and let it come to room temperature. Empty it into a bowl and clean it's mason jar or whatever you're using to store the starter.
Add to the starter
1 c warm water
1 c flour
Stir and leave covered several hours to proof. Leaving it overnight usually works well. You can always put the bowl in the oven with the oven light on. I usually leave it on the counter. The sponge should have a sour smell and a froth. If not, let it sit longer.
Once you're sponge has proofed (frothy and sour), add to another bowl
2 c of sponge
2 Tb oil
4 tsp sugar
2 tsp salt
Put the rest of the sponge back in the starter jar and return that to the fridge.
Get ready about 3 c of flour.
Mix the sponge, oil, sugar, and salt. Add flour 1/2 c at a time. You should begin kneading when it's less like batter and not quite so sticky. You can knead the dough in the bowl or turn it on out a floured counter.
When all the flour is incorporated and the dough is satiny (a few minutes), put the dough in a covered bowl and let it rise until doubled in bulk. This may take a while as it's the yeast in the sponge that's doing the work and it's not as disciplined as the yeast you get in a packet.
Once it's risen, punch the dough down and knead a little more. You can also flatten out the dough on the counter and then fold the dough in half, and fold it again a couple times. It's a little easier on your hands and wrists.
Form a loaf and set it on a lightly oiled baking sheet, a baking sheet with corn meal on it, or a piece of baking parchment on a stone or baking sheet. Leave in a warm place until doubled in bulk.
You can slit the top if you like and brush a mix of egg white and water on the top just before it goes in the oven. You can also put a bowl of water in the rack below where the bread will bake so the oven has some steam in it.
Place the loaf in a cold oven, and then turn on the oven to 350 and bake for 30-45 minutes. You'll know it's done when the crust is dark brown and the loaf sounds kind of hollow when you give the top a flick with your finger.
Cool on a rack or towel for about an hour. The crust should be crunchy/chewy for awhile, but will soften up overnight. Also, bread goes stale faster the more surface area it has. For example, a baguette-shaped loaf will go stale faster than a round loaf.
That's pretty much it. This is as basic as it gets, but you have to accept that you're dealing with a wild organism and you're results may differ wildly from other's. It may not work at all. But trying is better than not trying, so go make a mess.