Sift together the flour, baking soda, and salt into a bowl. Add enough to form a stiff dough. Knead the dough well on a lightly floured board, form into 4 or more equal-sized balls. Roll out the dough thinly to form 8-inch or 12-inch circles. Then brush on a thin coating of vegetable oil. Roll into balls again, cover, and allow to stand for 15 minutes at room temperature. Roll out the dough again and flatten to the original dimensions by patting lightly. Heat a cast-iron or heavy-bottomed frying pan so that when tested with a drop of water, it sizzles. Place the rotis, one at a time, in the pan and cook for a minute. Turn, and spread a thin layer of vegetable oil on the face of each roti, and turn frequently until cookedwhen brown flecks appear on the surface. Remove from frying pan and pound between the palms of the until it becomes supple. Keep rotis warm and moist by covering with a towel. Yields: 4-6 servings Notes from cookbook: Traditionally rotis are cooked on a flat iron grid called a tawa, but any heavy skillet or griddle can be used. If the roti is to be filled with any curried meat, poultry, or vegetable and eaten as a food, make 12-inch rotis. Place the filling in the center and fold in the edges. When they are to be served as a bread to dip up curries, chutney gravies, prepare 8-inch rotis. ----