If you don't have yeast, making your own sourdough starter is a great option if you have the time. A sourdough starter contains naturally occurring yeast, and forms bubbles in the dough to make it rise. It's made by combining flour and water, and while that sounds simple, this method actually requires a bit more patience as it takes at least five days to form. You can use one cup of sourdough starter to replace a two-teaspoon yeast requirement.
Here's a breakdown of all the steps to making your own sourdough starter.