Preheat the oven to 200 C / 400 F.
Place bones in a single layer on a sheet or roasting pan. Drizzle over with olive oil or coconut oil. Roast for 30 minutes, then flip each bone over and roast for an additional 30 minutes. This browns the bones and gives the stock its lovely colour and flavour. Chop the vegetables while the bones are roasted
Add the roasted bones, vegetables, vinegar, bay leaf, peppercorns and garlic (if using) in a large soup pot. Cover completely with water (about 2-2.5 litres) and bring to a high simmer
Once you have a high simmer, reduce the heat to low and let the broth simmer for 12-24 hours. If using a slow cooker, set it to LOW after you've brought the broth to high simmer first, and cook for the same time.
Throughout simmering, add more water as needed to keep all the ingredients submerged.
Once the broth has reached a dark, rich brown colour, remove from heat. Discard the bones, vegetables and bay leaf and strain through a cheesecloth. Cool the pot to room temperature
Once at room temperature pour into jars and let cool in the refrigerator for at least 1 hour.
When you are ready to serve, skim the condensed fat off the top of the broth and heat to the desired temperature