Combine the flour, water, teaspoon of salt, and yeast into a bowl. Stir until a shaggy mixture forms. Cover with plastic wrap and rest for 12-24 hours.
Put the empty cast iron pot (with the lid) into the cold oven. Turn the oven on to 450ºF and let the pot preheat with the oven.
While the pot is heating up, cut out a circle of parchment slightly bigger than the bottom of the pot. Take the shaggy mixture and put it onto the parchment, working it into a rough ball shape. Let rest for 30 minutes, while the pot is in the hot oven.
Slash an X shape into the top of the ball of dough and sprinkle with flaky salt. Take the cast iron pot out of the oven and remove the lid. Holding onto the parchment, drop the dough ball (with the parchment on the bottom) into the cast iron pot. Cover with the lid.
Place back into the oven and bake covered for 30 minutes, then uncovered for 15 minutes. Cool for at least 30 minutes before eating. Enjoy!