If using active dry yeast, add warm water, yeast, sugar and vinegar together to the bowl of a stand mixer, mix, and let sit until bubbly (about 3-5 minutes). (If using instant yeast, there's no need to let it sit.)
Add the salt and oil to the mixer. Mix, then slowly add the flour in.
If the dough is too soft or sticky, add more flour in, a ½ cup at a time, until the dough is soft but firm enough to mold into dough loaves.
Knead the dough for 2-5 minutes in the stand mixer. Put the bowl in the oven with a small pot of boiling water (to keep the dough moist). Watch the dough and punch it down when it gets to the top of the mixing bowl. Do this every time it gets to the top of the bowl, as long as you have time to babysit it (2-5 times).
Put the dough on a greased countertop and divide into 2 or 3 sections (makes 2 large loaves or 3 small). Spray a cookie sheet with cooking spray and sprinkle a thin layer of cornmeal on the bottom of the sheet. Roll the dough balls into rectangle/long French bread shapes. Slash tops of bread diagonally 3-5 times and cover with a beaten egg.
Let rise 30 minutes (or until doubled) on the counter and bake at 375°F for 30 minutes. If they are having problems rising, you can put them in your oven at 170°F and wait until they are the size you want to cook them at. Once they are at the right size, turn the temperature to 375°F (without opening the door!) and let them bake until done.