Add water and discard: Pour the warm water into a mixing bowl, then gently add the sourdough discard.
Add dry ingredients: Add the bread flour, salt, and yeast.
Mix: Mix with a dough hook for 3 to 5 minutes until a soft, sticky dough forms.
First rise: Place the dough in a lightly oiled bowl, cover, and let rest for 1 to 1 ½ hours.
Stretch and fold: With wet hands, stretch one side of the dough up and fold it over. Turn the bowl and repeat 4 times total.
Second rest: Cover and let rest for 2 more hours, until puffy and bubbly.
Shape: Turn the dough onto a floured counter and gently press or roll into a 14 x 10-inch rectangle.
Cut: Use a dough scraper to cut 7 to 9 equal rectangles.
Final rise: Place on a parchment-lined baking sheet, cover with a dish towel, and let rise until doubled.
Preheat: Heat the oven to 450°F.
Bake: Dust the tops with flour and bake for 12 to 15 minutes, until golden and crusty.
Cool: Cool on a wire rack before slicing.