Whisk fiercely for 30 seconds after adding the water and yeast to a small bowl. On top, the mixture ought to bubble. Alternatively, if it doesn't and the yeast granules float, the yeast is "dead" and needs to be thrown away. Start over with a new quantity of yeast and water.

With a rubber spatula, add the flour and thoroughly incorporate. It will have a thick texture, similar to thick pancake batter.

Clean the bowl's sides, wrap it in plastic wrap, and let it at room temperature for 18 hours. 30 minutes should be spent chilling before use.

If you are not using the starter right away, you can store it in the refrigerator, though I suggest keeping it for no more than 8 hours. Bring to cool room temperature before using.