Rinse the bones and place them in a large stock pot. Add cold water to the pot and bring it to a boil; roughly 30 minutes. Carefully drain the bones and rinse them under running water. If you're reusing the same stock pot, quickly wash it out to remove any scum.
Stock
Place the bones back in the stock pot and cover them with three quarts of cold water. Heat the stock over medium heat avoiding letting the stock boil. Reduce the heat as needed to keep it at a simmer. Gently skim the scum off the top as needed.
Trying not to aggravate the stock, slowly add in the onions, celery, and sachet. Add water as needed to keep the bones submerged.
Cooking times vary depending on the type of bones you add. See below for my recommendations.*
Strain
Remove the stock from the heat, skim away any scum, and gently add up to 2 cups of cold water. Let sit for 10 Minutes. Skim away any additional scum that rises to the top.
Carefully strain the stock through a fine-mesh sieve lined with several layers of cheesecloth and cool the stock in a food-safe way, like in a cold-water bath. This recipe should yield about 2 quarts of white stock.
Notes
The sachet is more or less the same as a bouquet garni. The difference is it helps contain any pieces that dissolve or break apart during cooking. This ultimately keeps down the amount of skimming you need to do.
*Recommended Cooking Times:
Turkey, ham, and chicken stock should simmer in the water for about 2-3 Hours.