In a large bowl mix together ground beef, minced garlic, bread crumbs, Parmesan cheese, onion powder and egg. Shape into 15 meatballs.
Place meatballs on a baking sheet that's been lined with aluminum foil or parchment paper (easy cleanup!). Bake in the oven for 15 minutes. Please don't skip this step if possible, it will prevent the meatballs from getting too greasy in the slow cooker.
In your slow cooker add a jar of your favorite spaghetti sauce, along with crushed tomatoes, tomato paste, brown sugar and a bay leaf.
Add meatballs into the sauce in slow cooker and mix so the sauce covers them.
Cook on LOW for 6 hours. After 6 hours, remove the bay leaf.
During the last 15 minutes, bring a pot of salted water to a boil and cook spaghetti according to box. Once cooked, drain and serve the spaghetti with meatballs and sauce!
Serve and enjoy! I like to add additional Parmesan cheese and parsley on top when serving.