Mix the ingredients for the initial sour. Cover and let rest at 75°F/24°C for 24 hours. The flour and water tend to separate overnight; recombine on the second day. Let rest for another 24 hours at 75°F/24°C.
On the third day, combine 4 oz/110 g of the initial sour mixture with the water for the first feeding and blend to fully combine; discard excess sour. Ble