How do you make yeast using bread?

Homemade Yeast Starter Take equal parts of flour and water, leave the mixture in a warm location. Then walk away and leave it along for a couple of days. When you return in a couple of days to look at it, the starter should be a frothy mixture. You'll see how the flour and water have developed. There should be some smelly water on top, and in general, you'll have a starter of wild yeast.