Skimming tips: use a large ladle held parallel to the surface of the stock. If you place the stockpot off center on the burner, fat and foam will accumulate in the coolest area, making it easier to skim. What is a stock bag? In restaurant kitchens, little is wasted, including vegetable scraps. Mushroom bottoms, tomato cores, zucchini and onion ends, etc., all tend to make their way into a chicken or vegetable stock simmering on the stove (at least one is going at all times) You can replicate this method by throwing such scraps into a ziptop freezer bag in the freezer, and using it to enhance and add complexity to chicken or veg stocks. Two rules apply: Not too much of ANY one vegetable, which would overwhelm the stock; and NO vegetables that are intensely strong or bitter (cabbages, broccoli, cauliflower, eggplant etc.) But bits and ends of squash, green beans, pea pods, tired lettuce leaves as well standard aromatic vegetables and those mentioned above are quite at home in the stockpot.