In an electric mixer with the dough hook, combine the flour, starter and salt, and knead until it no longer sticks to the sides or bottom of the mixing bowl.
Place a lightly oiled bowl, turning to coat. Cover with plastic wrap and let dough rise in a warm, draft-free place until doubled in size, 1 to 1 1/2 hours. Turn out onto a lightly floured surface. Sprinkle lightly with flour and knead gently, removing any large air bubbles. Knead into a small circle, then shape into a tight ball, pinching the seams together underneath. Place on a well-floured board or baking peel, seam-side down. Cover with a kitchen towels and let rest until doubled in size, about 1 hour.
Preheat a baking stone, if available, on the bottom rack of an oven at 400 degrees F. With a sharp, serrated knife, cut a large "X" or cross-hatch pattern into the top of the dough.
Spray lightly with a mister and transfer to the baking stone (or place on a heavy baking sheet lightly dusted with cornmeal) and bake until golden brown and the bread sounds hollow when thumped on the bottom, about 60 minutes. (Sourdough should have a darker crust than other breads, so leave in the oven 5 minutes after you think it is done.)
Remove the loaf from the oven and let cool on a wire rack for at least 30 minutes before serving.