1. Place onion in a 6-quart electric slow cooker coated with cooking spray; top with carrots and potatoes.
2. Combine broth, next 3 ingredients, 1/2 teaspoon salt, and 1/4 teaspoon pepper. Pour over vegetables.
3. Combine paprika, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon pepper; rub over chicken. Heat a large nonstick skillet over medium-high heat. Add oil to pan; swirl to coat. Add chicken. Cook 3 minutes on each side or until browned. Arrange chicken on top of vegetables.
4. Cover and cook on LOW for 3 1/2 hours or until chicken is done and vegetables are tender. Garnish with additional thyme, if desired.