Whisk flour, sesame seeds, yeast and salt together until well combined.
Add cool water and work into flour until a uniform dough has formed (no effort needed, just 1-2 minutes mixing)
Cover bowl with cling film and leave dough to rise in a warm room temperature place for 12-18 hours.
Lay flat a cotton (!) cloth and flour with flour and cornmeal.
Generously flour a work surface and dump the sticky dough onto the work surface with the help of a spatula.
Excessively flour hands and form a ball, then place ball on floured cloth.
Cover dough with cloth and cover with another kitchen towel and let rise for a second time in a warm place for 2 hours.
minutes before the 2 hours of the second rise are over, preheat oven to 450 F (230 °C) and place a cast iron skillet or a baking sheet in the oven to be heated to the same temperature.
Carefully take out the piping hot skillet or baking sheet, place your hand under the cloth and lift the dough with one hand and dump it into the skillet.
Cut a superficial cross into the middle of the dough and return everything into the oven and bake for 25 minutes or until golden brown.
Take out of the oven and immediately remove from skillet or baking sheet and place on a wire rack to cool.