This type of pre-ferment is known as a poolish because it contains flour, water, and instant yeast. It is easy to make. Simply mix the yeast, warm water and flour together; cover; let stand in a warm place overnight. The following day, it's ready to mix into the dough.
In the bowl of an electric mixer fitted with a whisk attachment, mix together and beat the ingredients until smooth. Cover with a clean dishtowel; let stand in a warm, draft-free place overnight.
Measure out the amount needed for the recipe and use as directed.