In a large bowl stir together the flour, yeast and salt. Add 1 1/2 cups of water, and stir until blended; the dough will be shaggy and sticky. Cover the bowl with a plate or plastic wrap and let it rest on the countertop for 18-24 hours at room temperature.
After that time the surface of the dough will be dotted with bubbles. Generously flour a work surface and scrape the mixture out onto it, gently folding it over itself once or twice, then transfer to a rimmed baking sheet that has been sprinkled with flour or cornmeal. Spread it out with your fingertips until it's a rough oval or rectangle (you may need to sprinkle the top with a little flour too, to keep it from sticking to your fingers), and set it aside while you get your toppings together and preheat the oven to 450°F.
Spread the crust with tomato sauce, barbecue sauce, pesto or anything else you'd like to sauce it with, then top with your choice of toppings and grated cheese.
Bake for 20-30 minutes, until bubbly and golden.