Mix flour, yeast and salt in a large bowl.Add warm water to the ingredients and mix until a sticky dough forms.Cover with a towel and let it rise on the counter for 12 to 20 hours.Preheat the oven to 500F/260C.Turn your dough out on a floured surface, it will be flat, tuck all four sides in to form a ball and place it on a floured towel seam side down, sprinkle with more flour.Let it rise for 20 minutes.If you are short on time you can bake your bread after a 20 minute rise and it will be a somewhat dense and hefty loaf yet still delicious. (Like mine in the pictures). Alternatively, you can let it rise for 2 more hours in order to produce a more airy loaf of bread.Preheat your oiled dutch oven with the lid on.Take it out of the oven and carefully place your dough in it, cover with a lid and bake for 30 minutes.Take the lid off and bake for 10-15 minutes longer to get more colour into your crust.