Heat oil in a skillet over medium heat.
Add ground beef. Cook until browned. Drain fat.
Transfer beef to your slow cooker carefully.
Add onion, garlic, and chopped cabbage on top.
Pour in beef broth, tomato sauce, and diced tomatoes.
Stir in rice, Worcestershire, paprika, and thyme.
Add bay leaf. Season with salt and pepper.
Cover and cook on low for 6 hours.
Stir halfway to keep rice from sticking.
Remove bay leaf before serving warm.