Preheat oven to 450F
Chop the garlic in half, crosswise.
Quarter the onion.
Chop the other veggies into 2-inch segments.
Bake the bones and veggies on parchment paper for 20 minutes.
Toss everything, bake for another 20 minutes, or until the bones are browned.
Scrape everything into a slow cooker, add the rest of the ingredients.
Cover with water, and simmer for 2 days.
Top up with water, as needed.
Strain, let cool to room temperature.
Put in individual containers, keep refrigerated, and consume within 1 week.