Cornflakes settle the way they do by turbulent particle sorting when the box is shaken, not by "gravity". Left alone the small cornflakes will stay put.
Both shaking and gravity are necessary wrt separating the cornflakes. You could shake a box of cornflakes all you like in zero gravity and there will be no separation. Molecules are constantly being shaken at any temperature above 0 deg K. Perhaps look up "Brownian motion".