In a large mixing bowl, combine the flour and salt (if using). Add the water and mix with a wooden spoon or your hands to make a soft dough. Cover with plastic wrap, let stand for 5 minutes, and then knead for about 3 minutes, until smooth. If the dough is too dry, wet your hands and continue kneading and wetting your hands until the dough is soft. (If the dough is too dry, the arepas will crack around the edges when you shape them into disks.) The dough is now ready to be shaped into standard arepas or to be mixed and kneaded with other ingredients.