Pour boiling water over liver until surface is whitened; drain. Dip in barley or rye flour, shaking off loose flour as it is lifted out. Put melted bacon fat in dripping pans to depth of one-half inch. Lay slices of liver in bottom of pans, sprinkle with salt and pepper; bake twenty minutes, or until done, in hot oven. The liver should be cooked through, but not hard and dry.