- Add the frozen Italian meatballs to the slow cooker. 
- Pour the marinara sauce over the meatballs, ensuring they are well coated. 
- Optionally, add minced garlic, Italian seasoning, and red pepper flakes for extra flavor. 
- Set the slow cooker to low for 4-6 hours or high for 2-3 hours. Stir once or twice during cooking. 
- Once done, check that the internal temperature of the meatballs reaches 160°F (71°C). 
- Serve over pasta, in a sub sandwich, or with your favorite sides. Garnish with Parmesan cheese, if desired.