Place beef stew meat, potatoes, sliced carrots, and chopped onion into a slow cooker. Sprinkle with salt, pepper, garlic powder, and Worcestershire sauce. Pour in beef broth, tomato paste, and cornstarch and stir.
Heat on low for 8 hours or on high for 6 hours. This beef stew does best cooking low and slow so I suggest cooking it on low for 8 hours.
Taste for seasoning and add more salt and pepper as needed.