In a large bowl, add 2½ cups lukewarm (85–90°F) water. Sprinkle the yeast over the top, then add the whole wheat flour and stir with a wooden spoon until fully incorporated. Cover with plastic wrap and set aside in a warm place until puffed and frothy, about 1½ hours.
Sprinkle the salt over the whole wheat mixture, then add 1 cup all-purpose flour. Stir well with the wooden spoon, then continue adding white flour in ½ cup increments, stirring until the dough is too stiff to continue (about 1½ cups). Generously flour a clean work surface, then turn the dough out onto it. Knead until the dough is smooth and supple, adding more flour as needed to keep the dough from sticking to your hands and the surface, about 10 minutes. (You might not need all of the flour.)
Clean out the bowl and coat the inside surface lightly with the oil. Return the dough to the bowl, cover the bowl with plastic wrap, and set aside to rise in a warm place until the dough has risen to slightly more than double its size, about 2 hours.
Meanwhile, set a pizza stone on the bottom rack of the oven and preheat to 450°F. When the dough has risen, lightly flour a work surface and turn out the dough onto it. Divide into 4 equal pieces, about 11 ounces each. Gently stretch each piece into a flat oval, about 6 inches wide and 4 inches long. Cover the ovals with plastic wrap and set aside to allow the gluten to relax slightly, about 20 minutes.
When the oven is hot, begin shaping the first bread. Place a small bowl of cold water at the edge of your work surface. Dip your fingertips in the water, and make tightly spaced, uniform indentations all over the surface of the first piece of dough. Stretch into a long oval strip by draping the dough over both hands and gently pulling them apart. The dough should gradually stretch and give until extended into a long oval, about 16–18 inches long. (There may be a few holes in the dough. That is okay.) Sprinkle the shaped dough with a ¼ teaspoon of nigella seeds, then, using both hands, transfer it onto the heated pizza stone and bake until the bread is slightly golden on the surface with a lightly browned bottom, 4–5 minutes. While the bread bakes, shape the next bread, so that when the first loaf comes out of the oven, the second one is ready to go. Continue baking the remaining loaves in this manner.
Transfer each to a wire rack to cool slightly. Then serve, or wrap the loaves in a dry cloth to keep warm before serving.