Preheat oven to 400°F (200°C). Rinse beef bones under cold water, pat completely dry with paper towels, then arrange in a single layer on a roasting pan.
Drizzle bones with 1 tablespoon olive oil, rub to coat evenly, and roast for 40–45 minutes, flipping halfway through, until deeply browned and caramelized.
While bones roast, roughly chop carrots and celery into 2-inch pieces, quarter the onion (peel on), and halve the garlic head crosswise; gather herbs and spices.
Transfer roasted bones and all pan drippings to a large stockpot; add carrots, celery, onion, and garlic, then pour apple cider vinegar over bones and let sit 15–20 minutes.
Add bay leaves, peppercorns, thyme, parsley, and sea salt to the pot, then pour in filtered water until bones are submerged by about 2 inches (5 cm).
Bring to a boil over high heat, then skim foam and scum from the surface every 10–15 minutes during the first hour for a clear, clean broth.
Reduce heat to the lowest possible setting so only a few bubbles break the surface, then partially cover and simmer undisturbed for 12–24 hours.
Check every 2–3 hours to ensure bones remain submerged, adding 1–2 cups of hot water as needed; avoid vigorous stirring to keep the broth clear.
Turn off heat, let broth cool 30 minutes, then ladle through a fine-mesh strainer (optionally lined with cheesecloth) into a large bowl; discard solids.
Cool broth to room temperature, then refrigerate 4–6 hours or overnight; remove or leave the solidified fat layer on top before reheating and serving.