In a large mixing bowl, whisk together flour, salt and yeast. Pour in warm water and stir mixture with a wooden spoon until a shaggy ball forms (you can add a little more flour if you feel it needs it). Cover bowl with plastic wrap and allow to rise for 12 - 18 hours (on the counter at room temperature).
Heat oven to 450 degrees. Once oven has reached 450 degrees, place a cast iron pot covered with lid into preheated oven, heat pot for 30 minutes.
Meanwhile, turn dough out onto a heavily floured surface then shape dough into a ball. Cover dough with plastic wrap and allow to rest while pot is heating. Remove pot from oven and with floured hands, carefully drop dough into hot pot (you DON'T need to grease the pot) cover with lid, then immediately return pot to oven and bake 30 minutes (at 450 degrees).
After 30 minutes, remove lid from pot and bake uncovered for 15 minutes. Remove from oven and allow bread to cool on a cooling rack. Once completely cooled, bread stores well in an open paper bag (it helps the bread maintain it's crisp crust. I wouldn't recommend storing it in an airtight container or ziploc bag).
I made a wheat version of this with 1 1/2 cups whole wheat flour, 1 1/2 cups bread flour, 1 tsp salt, 1/2 tsp yeast, 2 Tbsp honey combine with 1 1/2 cups + 1/3 cup warm water and rise and cook according to directions listed. It was delicious!