Rub birds with cut lemon, and salt and pepper them. Wrap with the bacon and tie securely with twine. Heat the fat and brown the birds.
Wash the drained sauerkraut (unless it is very mild, then just drain it). Place a layer of it with the apple slices in the bottom of a casserole and imbed the birds. Cover with the rest of the kraut and apple, add the liquid, and cover closely. Let simmer very slowly for about 2 hours.
Put the birds on a hot plate, and thicken the kraut with the flour. Make nests in it, and replace the birds in them, ready to serve.