Preheat oven at 350 degrees Fahrenheit. Line a large baking sheet pan with parchment paper. Finely chop green onion and mince garlic. Finely chop kale and measure out 1 cup.
In a large mixing bowl, combine ground chicken with vinegar and mix together. Sprinkle with Italian seasoning, oregano, parsley, pink sea salt, and black pepper. Toss in green onion, and garlic. Incorporate all the spices and herbs well with the ground chicken.
Toss in the rest of ingredients; kale, mozzarella cheese, egg, and flax meal. Mix well making sure all ingredients are well combined.
Using an ice cream scooper or spoon, scoop out ground chicken and start rolling into balls. You can make them as big or as small as you'd like. I usually roll them into about 1.5-2 inch wide balls and get about 12 meatballs. If you roll them into bigger balls, you may have to add more baking time so they can fully cook on the inside.
Place rolled meatballs on lined baking sheet pan and line them up in rows leaving about 1/2 inch to 1 inch space between them.
Place meatballs in oven and bake for 30 minutes.
Remove meatballs from the oven and serve immediately while still hot. Serve with spaghetti, spaghetti squash noodles, or zoodles, any preferred sauce, or in any other way you wish to serve them. Enjoy!