Mix the yeast and 2 1/2 cups of water in the bowl of a stand mixer and set aside for 10 minutes to get the yeast working. It should become frothy.
Add the sourdough, flour, vital wheat gluten, and salt. Using the paddle attachment on your stand mixer, mix until everything is combined. You should have a batter that's just slightly thicker than a pancake batter. If it's too dry, add the remaining cup of water a little at a time and keep mixing.
When the dough starts to rise on the paddle and makes a flapping sound, remove the paddle attachment and replace it with a dough hook.
Knead on medium speed for about five to seven minutes or until the dough comes cleanly off the sides of the bowl.
Pour the dough into a bowl or large bin coated with oil. It will be very loose, but that's how it's supposed to be. The container should be large enough to hold the dough once it has risen to about three times its size. Spray some oil on top of the dough to keep it from drying, then cover the bowl with a kitchen towel, put a rubber band around it to hold it in place, and leave overnight or for eight hours on the kitchen counter.
By morning the dough would have risen quite a bit. Sprinkle a large cookie sheet or two smaller ones with lots of flour. Turn the dough out into the sheet and cut into half with a bench scraper or a knife.
Flour your hands and shape the loaf into a rectangular shape using your fingers and the bench scraper. Tuck the ends underneath so you get as even a shape as possible, although your bread will still look very rustic. You don't want to deflate the dough too much by overhandling it.
Dust some more flour on top of the loaves, then cover them loosely with kitchen towels. Put in a warm place to rise, about 90 minutes.
Half an hour before you bake the bread, put a pizza stone in the oven and preheat it to 500 degrees. If you don't have a pizza stone, don't worry-- we can do without. Place an empty pan in the bottom rack of the oven.
After 90 minutes of rising, the loaves should be puffy and should have doubled in size. Now place them in the oven and immediately add a cup of hot water to the empty pan you placed earlier in the bottom rack.
Close the oven and let the bread bake undisturbed for about 28 minutes or until the bottom sounds hollow then tapped.
Remove to a rack and allow the loaves to cool completely before eating.