Prepare the liver by washing thoroughly in tepid water and removing any tubes. Dry well, cut into slices ¼ in. thick and toss in the seasoned flour. Cut the bacon in pieces, slice the onions thinly, slice the potatoes. Place alternate layers of liver, bacon, onions and potatoes in a pie-dish or casserole and sprinkle with sage and seasoning. Add enough stock barely to cover the contents and place a thick layer of sliced potato on top. Cover with a lid and cook in a moderate oven (350° F., Gas 4) for about 2 hr. Remove the lid ½ hr. before serving, place small pieces of dripping on top and allow the potatoes to brown. Sprinkle with chopped parsley.