Add the beef cubes, carrots, potatoes, onion, and garlic to the slow cooker.
In a small bowl, whisk together the beef broth, tomato paste, flour, thyme, salt, and pepper until smooth.
Pour the broth mixture over the meat and vegetables in the slow cooker.
Cover and cook on low for 8 hours until the beef is tender.
Cut the tops off each mini pumpkin and scoop out the seeds and strings.
Ladle the hot stew directly into the hollowed pumpkins and serve right away.