Pat the chicken legs dry with paper towels.
Season generously with salt and pepper, then place in a dish or zip-top bag with garlic, thyme, and bay leaves.
Refrigerate for at least 12 hours or overnight to marinate.
Preheat oven to 275°F (135°C).
Wipe off excess salt and herbs. Place chicken legs in an oven-safe dish and cover completely with duck fat or oil.
Bake for 2.5 to 3 hours until meat is fork-tender.
Remove chicken from fat and crisp skin in a hot skillet before serving, if desired.