Activate yeast in water:

In a large bowl, combine 1/4 teaspoon fresh yeast (or 1/16 teaspoon dry yeast) with 1 cup room temperature water. Stir and allow to rest for 2 minutes to activate.

Mix flour into yeast:

Add 1 cup all-purpose flour (or bread flour) to the yeast mixture and stir with a spatula for 2-3 minutes until the mixture is smooth and no lumps remain.

Ferment poolish:

Wrap the poolish bowl with plastic wrap to avoid drying and let it ferment at room temperature for 8 hours. If you plan to use it after 12 hours, let it sit at room temperature until bubbling begins (30 minutes to 1 hour), then transfer to the refrigerator.