Cut roast in half. In a small bowl, combine the garlic powder, thyme, ginger and pepper; rub over roast. In a large skillet over medium heat, brown roast on all sides in oil.
Place roast in a 5-qt. slow cooker. In a small bowl, combine the broth, sugar, lemon juice, soy sauce and orange peel; pour over roast. Cover and cook on low for 4 hours or until a meat thermometer reads 160 degrees F. Remove roast and keep warm. In a saucepan, combine the cornstarch and orange juice until smooth; stir in cooking juices. Bring to a boil; cook and stir for 2 minutes or until thickened. Serve with the roast.