Pour the jar’s contents, water, and vinegar into a mixing bowl.
Stir until no dry patches remain, and a ball of dough can be formed. No need to knead!
Cover the dough ball with a kitchen towel and let it rise in a warm, room-temperature area of your kitchen for 1½-2 hours. It should double in size.
Preheat the oven to 450°F. If using a baking stone or cast iron, preheat that as well.
Punch the dough, remove it from the bowl, and turn it onto a lightly floured surface.
Using your hands, pull down the sides until the dough forms a round loaf. It will be more rustic and less elastic than a typical loaf because we’re skipping the kneading portion.
Place on a piece of parchment. Let rest for 40 minutes.
Before baking, dust the top with a small amount of flour and gently rub it over the surface. Slash it with a bread lame into any pattern you’d like.
Remove the stone or cast iron from the oven and carefully transfer the dough with the parchment onto the baking stone.
Bake for 30 minutes, uncovered, or until golden brown on top.
Let cool completely on a wire rack before slicing and eating.