Classic Slow Cooker Pot Roast with Gravy Recipe

**Ingredients:** - 3-4 lbs beef chuck roast - 1 tbsp olive oil - 1 tsp salt - 1 tsp black pepper - 1 tsp garlic powder - 1 tsp onion powder - 1 tsp dried thyme - 1 tsp dried rosemary - 1 cup beef broth - 1 cup water - 2 tbsp Worcestershire sauce - 4 medium carrots, peeled and cut into chunks - 4 medium potatoes, peeled and cut into chunks - 1 large onion, cut into wedges - 3 stalks celery, cut into chunks - 2 tbsp cornstarch (for gravy) - 2 tbsp water (for gravy)