Combine all ingredients except cooking fat in a large mixing bowl. Stir together using a large spoon until the mixture is uniform, about 1 minute. Shape into a rough 3-inch disk, cover in plastic wrap and chill in the refrigerator for at least an hour.
Remove dough from the refrigerator and divide into 6 equal pieces. Roll into balls and flatten into thin 4-inch discs with a rolling pin.
Heat a couple of teaspoons of butter or olive oil in a 12" non-stick skillet over medium-high heat until melted and bubbling has subsided (if using butter) or until shimmering (if using oil). Place 2 or 3 pieces of flatbread in the skillet and cook until spotty brown, about 2 minutes. Flip and cook another 2 minutes on the second side. Transfer to a wire cooling rack and cook remaining pieces.
1) you can substitute whole wheat flour for the spelt - I just happened to have spelt flour on hand (spelt is an ancient form of wheat but has less gluten); 2) you can use plain whole yogurt in place of the Greek yogurt but the dough will be much stickier, so be sure to generously flour the board and rolling pin; 3) this is a great time to pull out your griddle if you have one and cook all of the flatbread at once. Simply preheat to 400°F, very lightly oil the surface and cook about 2 minutes each side.