Add remaining 2 tablespoons oil to Dutch oven; heat over medium. Add onion, shallots, carrot, celery, and remaining 1 teaspoon salt. Cook, stirring occasionally, until vegetables soften and begin to brown, 10 to 12 minutes. Reduce heat to low. Add garlic and thyme; cook, stirring often, until garlic is fragrant, about 1 minute. Stir in wine, orange juice, honey, vinegar, and orange peel strips. Nestle lamb, fat side up, on vegetable mixture; bring to a boil over medium. Remove from heat and cover Dutch oven. Transfer to preheated oven and roast until lamb is fork-tender, 2 hours to 2 hours and 30 minutes.