Succulent slow-roasted leg lamb with garlic and rosemary

Ingredients

• 1 (4-5 lb) leg of lamb, bone-in, trimmed
• 6 cloves garlic, peeled and halved
• 2 tablespoons fresh rosemary leaves, finely chopped
• 2 tablespoons fresh thyme leaves
• 2 teaspoons kosher salt
• 1 teaspoon freshly ground black pepper
• 1/4 cup olive oil
• Zest of 1 lemon
• 1 large onion, cut into wedges
• 3 large carrots, cut into chunks
• 3 celery stalks, cut into chunks
• 1 cup dry white wine or low-sodium chicken broth