In a large mixing bowl, combine flour, wheat germ, oats, baking soda, and sugar. Add buttermilk or yogurt and salt. Stir until smooth. Spread in a greased 9"x13" jelly-roll pan. Bake at 350 degrees for 25-30 minutes or until golden and done. Cool on a wire rack. When completely cooled, break into chunks. Whirl in blender or food processor until crumbly. Spread on two large baking pans and bake at 250 degrees for about 25-30 minutes, or until cereal is very crisp. Cool on wire racks. Store in an airtight container when completely cool.