Combine the panko breadcrumbs, garlic powder, dried oregano, kosher salt, black pepper, and parmesan cheese in a large mixing bowl.
Mix in the grated white onion, eggs, and Worcestershire sauce.
Add the ground pork and mix until well combined.
Form the ground pork mixture into 24 evenly-sized balls. Place the meatballs on a rimmed baking sheet.
Transfer the baking sheet into your oven and broil under high heat for 8-10 minutes (or until brown). Then, flip the meatballs over and broil for another 2-3 minutes (or until brown) and then remove them from the oven. Keep an eye on them during this step to make sure they don't burn.
Pour 1 jar of marinara sauce into the bottom of your slow cooker.
Arrange the browned meatballs in an even layer on top of the sauce. It's okay if you don't have enough room and have to stack a few of them.
Pour the second jar of marinara sauce over top of the meatballs.
Place the lid on your slow cooker and cook the meatballs for 3-4 hours on high or 5-6 hours on low (until cooked through).
Serve the meatballs while they're warm, and enjoy!