In a 2 quart Pyrex measuring bowl (or large bowl), combine flour, yeast and salt. Pour vinegar, beer and water over the dry ingredients, then, using a fork, mix thoroughly until a shaggy dough forms. Cover the bowl tightly with plastic wrap, and let sit at room temperature for 18 - 24 hours. The dough should rise to the 7 cup mark on the bowl.
Scrape the dough onto a lightly floured work surface, and sprinkle with a little extra flour. Using your hands, gently pat the dough into a rectangle approximately 10" wide by 8" high. Sprinkle with flour as needed if the dough is sticking. Gently fold the dough over itself like folding a letter. Turn 90 degrees, gently pat to a rectangle and fold again. Then shape the dough into a ball by pulling edges into middle. Place dough in the center of a large sheet of parchment paper, then lift and lower into a 4-quart cast-iron dutch oven. Cover loosely with plastic wrap, and let rise for 2 hours.
Set an oven rack to the middle position. Uncover the dough, sprinkle the surface with a little flour, and using a sharp knife, make 3 parallel slits across the top of the dough about 1/2-inch deep. Cover the pot with its lid, and place in the cold oven. Heat the oven to 425°F, and when this temperature has been reached, let cook for 30 minutes. After the 30 minutes have elapsed, carefully remove the lid and continue to bake until the loaf is a deep brown (about 30 minutes longer). Using the parchment overhang, carefully remove the bread from pot, then transfer to a wire rack and let cool completely (about 2 hours).