In a glass measuring cup or microwavable bowl, heat water in the microwave for 20 seconds; this should result in a temperature of 80-90F.
If you're using Fresh or Active Dry Yeast, mix the yeast into the water and let sit for 2 minutes. If you're using Instant Dry Yeast (IDY), proceed to the next step. Note: Caputo yeast is labeled as Active yeast, but does not need to be activated in water (works as IDY).
Add the flour and yeast (if using IDY) to a large bowl. Slowly pour the water (preferment section only!) into the bowl of flour and mix well with hands, or a spoon, until fully incorporated and no dry flour remains. It will be a very shaggy texture and will not form into a dough - don't worry, this is what we want!
Cover the bowl with saran wrap tightly. Poke a small hole in the center of the film with a pen. Allow to sit at room temperature for 18-24 hours.