Place the meat in a large mixing bowl, add the egg, and almond flour, onion powder, garlic salt and herbs and mix well with your hands. Mix until just combined together - do not overmix.
Line a large baking sheet with parchment paper and preheat the broiler. Form the meat mixture into tablespoon-sized balls and arrange on the baking sheets.
Broil 2-4 minutes to lightly brown and release a small amount of fat.
Add all sauce ingredients, except the spinach, to the slow cooker and mix. Gently add in the meatballs and stir carefully.
Cover and cook for 4 hours on low.
Once ready, stir in the spinach and serve over spaghetti squash, roast veggies, potatoes etc.