In a clean 2 gallon plastic container, mix the potato water, flour and sugar with a wooden spoon.
Cover the container with plastic wrap and secure with a large rubber band.
Allow the mixture to sit for 24 hours at cool room temperature, approximately 70-75°F.
For days 1-3, stir the starter once every day for three days. Make observations of how it looks and changes.
On day 4, the starter will separate and smell quite sour. This is from the natural bacteria beginning to outnumber the yeast. Feed the starter 1 ¾ cups bread flour and 2 cups water at approximately 78° F. This will provide food for the yeast to multiply.
On days 5 through 8, allow the starter to sit at cool room temperature for four more days. Do not stir. Make observations.
On day 9, begin to feed the starter a regular maintenance schedule of 3 feedings per day, approximately every 4-6 hours.
On days 9 through 11, after the last feeding for the day, the starter is covered and left alone overnight. It should look nice and bubbly showing that it is active. Every morning, discard all but 2 cups of the starter. Save the starter in a liquid measuring cup while you wash the 2 gallon container out. Place the starter back into the clean, 2 gallon container and feed it. Begin 3 feedings using 1 cup of water (78°F) and 1 ¼ cups bread flour every 4-6 hours.
On day 12, the starter is ready to bake with. Just be sure to use it while it is bubbly and most active between 12 and 15 hours after its last feeding.