Add all ingredients to a large soup pot or your pressure cooker/Instant Pot then cover with water. If the veggies or bones are frozen, add some water and simmer until you can push it down into the pot.If you are using a pressure cooker, be sure to stay below the max fill line! Place the lid on your pressure cooker and set it to seal. Set the Instant Pot to pressure cook on high for 1 to 2½ hours. The longer the better if you are using carcasses or bones!
After the timer goes off, allow it to naturally release pressure. (If you don't have time, wait five minutes and go ahead carefully with a quick release.)
Set the Instant Pot to simmer for thirty minutes over medium heat with the lid off to reduce the broth. The more the broth reduces the more flavor it will have. You may have to set it to simmer a couple of times if your pressure cooker has a simmer time limit.
Place a large colander, over a large stock pot or container. When the soup has reduced, carefully ladle the bones and scraps into the colander in batches to strain. Set the garlic cloves aside. Use a large spoon to mash the broth out of the veggies. Continue until the stock pot is lite enough to pick up and pour through a colander into another large soup pot to finish straining. Careful! It will still be hot! Use oven mitts! The colander will be hot too!
Clean out your empty pot. Place a large fine strainer over it and strain the broth back into the Instant Pot. This will get out any residual scraps and make the broth a bit clearer.
For a more clear broth, pour the stock through a strainer back into the stock pot to build the soup. Taste and adjust for salt, and pepper. If it's a bit watery, continue to simmer until it's reduced and more flavorful.
Defat the broth with a defatting cup, or for easy cleanup, use a paper plate and skim off the fat that is collecting at the top.
FLAVOR BOOST! If you are a fan of garlic, squeeze the garlic out of the peels and smash it with a fork until smooth. Add it back to the pot and stir. If you don't like a lot of garlic, save it for something else, or just use a couple of cloves!
At this point, I like to divide it into several two-cup storage containers. I like the vented-lid two-cup storage containers. I cool them quickly by putting them outside in the winter, or filling the bottom of the sink with cold water and ice and gently placing the containers inside, being careful not to get sink water in the soup.