Since there was sufficient interest, here are the detailed instructions for how I make sourdough bread. I will blast through the recipe, and annotate with comments at the end. I've tried to keep everything as brief as possible. There are photos of each key step leading to the loaf pictured above. Feel free to ask questions about anything.
Makes 2 1-pound loaves (approx.)
Step 1. In a large mixing bowl, mix well:
400 g active sourdough starter - see Annotations below if you don't have this (Photo: Active Starter)
400 g water
300 g whole wheat flour
350 g bread flour
Once mixed, let rest (covered) for 30-60 minutes (Photo: Initial Mix)
Step 2. Add:
21 g salt
50 g water
Mix well. Transfer to a different nonmetal bowl (or proofing tub if available). (Photo: Ready to Rise)
Step 3. After one hour, perform several "stretches" on the dough (Photo: Stretching the Dough). Repeat this 4-6 times (waiting 30-60 minutes each time), until dough has approximately doubled in volume, and bubbles are visible throughout (Photo: After Rise). See notes on Temperature in Annotations.
Step 4. Place dough on lightly floured countertop (Photos: Ready to Shape, See the Bubbles). Divide in two, and perform stretches and folds to shape into a ball (Photo: Initial Shaping). Let rest 30-60 minutes
Step 5. Gently stretch out, and stretch and fold into a final ball, and place into a flour-dusted bowl or basket "tighter-side" down (Photo: In Basket). Cover and put into the refrigerator overnight.
Step 6. In the morning, put a dutch oven (or similar all-metal pot with all-metal lid) into the oven. Preheat at 500 degrees for 30 minutes - you want this pot to be hot before the bread goes in it. NOTE: in the next step, ideally you are going to bake the bread on the pot's LID, and cover the bread with the pot's BOTTOM.
Step 7. Pull out lid from oven, turn over, dust with flour, and place dough upside-down on lid. Score top of dough with razor blade (Photo: Scoring). Put the pot bottom over the bread, and place into the oven for 15 minutes.
Step 8. Pull off the pan "bottom", leaving the bread on the lid in the oven (Photo: Remove the Lid). Reduce the temperature to 450 degrees and bake for another 15 minutes.
Step 9. Pull out bread from oven, dust off excess flour, and cool on a cooling rack. (Photo: Out of the Oven)
That's all there is to it! But of course, as they say, the devil's in the details, so unless that's enough to get by with, read on...
Measurements - forget the cups!
You'll see that all measurements are given in weight (grams). Get a scale that measures down to the gram, preferably one with a zero (tare) function. This helps ensure consistent amounts of ingredients in the recipes.
The basic way sourdough bread is made is by mixing flour, water, and salt with sourdough starter. The starter itself is just flour and water that has had enough time to develop a nice environment for yeast and bacteria to stabilize as an active culture.
Starter takes from 1-2 weeks to become healthy enough to use to make bread. There are kits you can get in some stores or online, or you can make it from scratch. I made mine from scratch, with the following recipe:
Day 1: Mix 300g bread flour with 300g spring water. Mix well in a nonmetal bowl, cover with a cloth, and set out near an open window
Day 2: Stir mixture
Day 3: Stir mixture
Day 4: Stir mixture - you should be seeing some bubbles at this point. You don't need to keep it near the window anymore if you do. If no bubbles, you may need to try again starting with Day 1
Day 5 - 7: Every day, throw away half of what you have, and stir back in 150g bread flour and 150 g water - this is a "feeding" (basically doubling the existing starter with new flour/water)
Day 8-14: Twice a day (every 12 hours): throw away half of what you have, and stir back in 150g bread flour and 150g water
At this point, the starter should get very bubbly and double in volume a few hours after feeding it. When the recipe calls for "active" starter, this is what is meant. Note that if you left your starter out longer without feeding it, it would lose bubbles and take on a more paint-like smell.
Note - an appropriate starter temperature during this is between 60 and 90 degrees F. If it is getting hotter than that near the open window, find a cooler place in the house.
After the starter has gone through 14 days (some say you can stop after 7), it can be stored in the refrigerator (with a lid) until you want to use it. Or leave it out (covered) as long as you feed it twice a day (I've kept mine out for about a year now - it went in the refrigerator only once when I was on vacation). If you put it in the refrigerator, it only needs to be fed about once a week. If you keep it in the refrigerator, and you want to make bread, take out 100g or so, feed that 100g with 150g water and 150g flour, and after a few hours (or overnight), you'll have your 400g starter for the recipe.
As indicated, the starter (and in fact the entire recipe) is temperature sensitive. If your dough is at 65 degrees, it will rise more slowly than at 85 degrees. If you want to control how quickly the bread rises, create the right temperature environment. For example you can turn on just your oven light in your oven, and get a nice warm environment for rising. But be careful, don't let the dough get over 90 degrees.
Hydration is measured by the ratio of water to flour in the recipe. In our case that number is 450/650 or about 70%. This is higher than most breads you might bake so you will see that the dough is stickier than most bread doughs (tip: best way to handle sticky dough is with wetted hands). But the higher hydration makes for a nice moist crumb. Experiment with different levels of hydration to find what works best for you.
Salt inhibits the rising action somewhat, but is essential for taste. Experiment with the amount of salt to your taste.
Stretching the dough
Dough stretching helps the dough build strength (and thus be able to rise and hold air well). You'll notice the strength increase as you stretch it. Be careful and stretch slowly to minimize popping bubbles that have formed and to minimize any dough tears.
If you let it, the dough will rise to 3x, or even more, of its original volume. Don't let it. Just give it the time to rise about 2x (about 4 hours or so depending on temperature). Then move on to the next step. The reason for this is you want the dough to have sufficient rising strength during the baking. Once you've risen the right amount of time, and given good dough stretches along the way, the dough will be teeming with bubbles (many visible through the dough), but still have lots of rising power at bake time. (Photo: See the Bubbles)
Scoring the bread helps control how the bread rises. Experiment with different scoring patterns - it will actually impact the final shape of the loaf.
Notice that you are baking in a closed pot. This is to give moisture to the dough during the first part of the baking - CRITICAL to getting a good rise. This is similar to "no knead" bread recipes, which you can read about online or see on Youtube. (Note - you don't have to cook ON the lid, but this is the easiest way to do it without burning yourself while scoring the bread.)
The lid is removed halfway to ensure a crunchy crust.
Feel free to experiment with everything in the recipe once you've got something as a baseline. Try different flours, additions, ratios, baking times, shapes, etc.