Creating Slow Cooker Salisbury Steak Meatballs is straightforward when you follow these simple steps:

1. Prepare the Meatball Mixture: In a large bowl, combine ground beef, breadcrumbs, Parmesan cheese, egg, chopped onion, minced garlic, Worcestershire sauce, salt, black pepper, onion powder, and garlic powder. Mix until well combined.
2. Form the Meatballs: Shape the mixture into meatballs, about 1-inch in diameter. Place them on a baking sheet lined with parchment paper.
3. Brown the Meatballs (Optional): In a skillet over medium heat, add a little oil. Brown the meatballs on all sides for added flavor. This step is optional but enhances the taste.
4. Prepare the Slow Cooker: Transfer the meatballs to the slow cooker.
5. Add the Gravy Ingredients: In a separate bowl, mix together the beef broth, sliced mushrooms, and ketchup. Pour this mixture over the meatballs in the slow cooker.
6. Cook: Cover and cook on low for 5-6 hours or on high for 2-3 hours, until the meatballs are cooked through and tender.
7. Thicken the Gravy (Optional): If you prefer a thicker gravy, mix cornstarch with water to create a slurry. Stir it into the slow cooker during the last 30 minutes of cooking.
8. Serve: Once cooked, gently stir the meatballs and gravy before serving.

These steps will guide you in creating this incredible dish effortlessly.