Bring leg of lamb to room temperature, about 2 hours.
Pour wine into a slow cooker. Mix lemon juice, honey, mustard, garlic, vinegar, rosemary, thyme, sea salt, and pepper together in a bowl until a thick paste forms. Massage paste into the lamb using your hands; gently place into the slow cooker.
Cook on low, without removing the cover, for 5 hours. An instant-read thermometer inserted near the bone should read 145 degrees F (65 degrees C). Let lamb rest for 15 to 20 minutes.
