Step 1

Combine salt, whole wheat flour, and 3 cups all-purpose flour in a large bowl. Whisk yeast, sugar, and 1¼ cups warm water in a medium bowl and let sit until foamy, about 5 minutes. Make a well in center of dry ingredients and pour in yeast mixture, then 2 Tbsp. oil. Mix with a wooden spoon until a shaggy dough forms; turn out onto a work surface and knead dough, dusting with all-purpose flour as needed, until dough is smooth, firm, very elastic, and no longer sticky, 8–10 minutes. Place in an oiled large bowl, cover, and let sit in a warm spot until doubled in size, 60–75 minutes.

Step 2

Punch down dough, turn out onto work surface, and divide into 12 equal pieces. Roll each piece into a ball; place on a lightly floured rimmed baking sheet. Dust tops of balls with flour; cover loosely with plastic wrap. Let sit in a warm spot until nearly doubled in size, 45–60 minutes.

Step 3

Prepare a grill for medium-high heat. (Alternatively, heat a dry large cast-iron skillet over medium-high.) Working with 1 ball of dough at a time and keeping remaining balls covered, roll out on a floured surface to a 7" round. Grill until puffed and blistered in a few spots but still soft, 45 seconds per side.

Step 4

Do Ahead: Dough can be made 1 day ahead. Let rise before proceeding. Cover and chill. Flatbread can be cooked 30 minutes ahead. Let cool slightly, then wrap in foil and keep warm in a 250° oven.