Heat the oven to 400°F and grease a baking dish with olive oil.
In a medium bowl, add the ground beef, spinach, coconut flour, oregano, salt, garlic powder, onion powder, and egg, and use your hands to mix until combined.
Use hands to shape the meat into golf-sized balls. Add the meatball to the greased baking dish and continue until all meat is used. Bake for 20 minutes.
While the meatballs are baking, add the marinara to a small saucepan and bring to a boil. Turn heat to low and simmer for 5 minutes.
Once the meatballs are baked, take them out of the oven and remove excess grease.
Add the marinara sauce to the meatballs and bake for an additional 5 to 10 minutes.