Add all ingredients to large stock pot. No need to be fancy here, I simply rinse the carrots and celery, snap them in half with my hands and toss in pot. I don't bother to peel the onions or garlic, just cut to expose flesh and toss in pot.
Cover everything with water, I just happen to have a very large stainless-steel stock pot (shh! don't tell my mom hers is missing), so I usually add 12-16 quarts of water. Then simply BTB/RTS (bring to boil/reduce to simmer) and simmer a good 4 hours or so. Until it tastes rich and yummy.
Strain out the bones, veggies and herbs - I do this by placing a strainer over another large pot(s) or a commercial food container commonly referred to as a Cambro container (Cambro is a brand name but is used to interchangeably to refer to the type of container - these can be purchased on Amazon and are also great to rising dough)
Next you could process the hot stock through a gravy separator to remove the fat and process immediately into canning jars. OR I find it much easier to place the stock in refrigerator overnight which allows the fat to rise to top and harden, then simply skim off with a large spoon.
After it's sleep over in the fridge, I bring the stock back to boil.
Fill prepared canning jars, place in pressure canner and process at 11 pounds for 20 mins for pints and 25 minutes for quarts (note: I live in Midwest, please adjust canning pressure/times to your altitude).
Serving Size 8 to 16 quarts