Step 1

Preheat oven to 450°F. Line a baking sheet with aluminum foil. Place beef bones on baking sheet, and drizzle with oil; toss to coat, and arrange in an even layer. Roast until bones are lightly browned, about 20 minutes.

Step 2

Using tongs, transfer roasted bones to a large stockpot. Add cold water, onion, carrots, celery, garlic, thyme, bay leaves, and peppercorns. Bring to a gentle boil over medium, skimming foam and fat often, about 30 minutes. Reduce heat to low; simmer, uncovered, skimming surface occasionally, until stock is rich and fragrant, 8 hours more.

Step 3

Line a fine-mesh strainer with cheesecloth and set over a large heatproof bowl. Carefully ladle bone broth through strainer into bowl until majority of the liquid is gone. Using tongs, discard bones, leaving cooked vegetable in the pot. Pour vegetables and remaining liquid into the strainer, pressing with the back of the ladle on the solids to extract remaining broth. Return stock to stockpot, and discard solids in strainer.

Step 4

If desired, simmer stock over low to reach desired concentration. Season to taste with kosher salt if eating as bone broth, or leave unseasoned to use as stock in recipes.