Preheat the oven to 400°F. Place bones on a parchment lined, rimmed baking sheet along with onion, garlic, and carrots.
Roast for 45 minutes (this will help give the broth added depth of flavor).
Transfer bones and vegetables to a large pot. Add cold water to fully submerge all ingredients, about 1 to 2 cups. Add bay leaves, cover with the lid slightly ajar, and bring to a very low simmer. Let simmer for 12 to 24 hours, skimming any excess fat off occasionally. The bone broth is ready when it's caramel in color and flavorful.
Using a mesh sieve, strain liquid to remove solids. Salt and pepper to taste, and store in airtight containers. This bone broth can be stored for 5 days in the fridge or up to 6 months in the freezer.