Slow Cooker Chicken Noodle Soup

Name: Slow Cooker Chicken Noodle Soup
Ingredients: 1 medium yellow onion; 4 medium carrots (about 12 ounces total); 2 large stalks celery; 6 bone-in, skin-on chicken thighs (about 2 1/2 pounds total); 3 large sprigs fresh parsley; 2 large sprigs fresh thyme; 1 dried bay leaf; 1 teaspoon kosher salt, plus more as needed; 1/2 teaspoon freshly ground black pepper; 1 (32-ounce) carton low-sodium chicken broth (about 4 cups); 4 cups room temperature water; 6 ounces dried spaghetti; 1/2 medium lemon; 2 large sprigs fresh dill