This is the recipe I used. Actually got it off a Lotus car forum.
You need some ingredients:Flour
If you can manage to find that, then you need some equipment:
Fork or other mixing tool
Jar with lid
Not too difficult so far, huh? Lets get started. Sourdough is sour because the culture is a mix of bacteria and yeast living in a symbiotic arrangement. So, you need a culture to get started. I suppose you could buy one, buy why, when it is free? Mix one cup of flour with one cup of water until you have a batter. Leave uncovered (if bugs are not a problem in your kitchen) and let it set for a while someplace warm like on top of the refrigerator, water heater, whatever. After a couple of hours, you can cover it with a towel. Let it sit for a day or two until it is bubbly (full of little bubbles). This is your Starter (sourdough starter, not Toyota starter.) Take 1/2 of your starter and put it in a jar with some more 1/2 flour and 1/2 water mix. Place in the refrigerator. This is what you will use for your next loaf of bread, replacing what you use with 1/2 and 1/2 flour/water.
Now we make Sponge. Take the other half of your starter (or 1/2 of your starter from the refrigerator if you are making it the second time) and add 1 cup water and 1 cup flour and mix well. Cover and let sit someplace warm for a while until it is bubbly (four hours to a day).
Now for the dough. Add in 3 cups of flour, two teaspoons of salt and enough water to make a dough (a cup or so). Add too much water? Just add a little more flour. Mix it all up well until it is like bread dough. I like to have it a bit more watery than other bread doughs. I mix mine in the automatic bread maker set to dough, but mixing by hand will work fine. Recommended but not necessary: take the bread pan and spray it with the non-stick agent of your choice (I use Pam). Then pour the dough into the pan. Cover and let sit someplace warm for a while (fastest I have observed: 4 hours, slowest: 2 days, typical: 24 hours) until it rises up to about the top of the pan or a little more or you get tired of waiting. Place in the oven preheated to 375 for about 35-45 minutes.
That's it. Pretty simple, huh? And nothing to it but flour, water and some salt. I would call that all natural. For the next loaf, just use 1/2 the starter from the 'fridge and start with making sponge. I have had my starter sitting in the fridge for three months without problems. If it goes "bad" and gets all nasty looking, just take out some that still looks OK and add it to some 1/2 and 1/2 flour/water and let it make starter again. I also like to pour off all the water on the top of the starter before I take out my culture for the sponge. If you smell it, it smells a lot like alcohol, and I figure that the yeasty guys work better if you don't get them drunk first.
My dough rises better if I add a little sugar or molasses. Do NOT add sugar to the starter (only flour and water).
Every sourdough starter will taste different. It all depends on the yeast/bacteria living in your area.