Preheat your oven to 375°F (190°C).
In a mixing bowl, combine the ground beef, almond flour, Parmesan cheese, egg, minced garlic, Italian seasoning, salt, and pepper. Mix well until all ingredients are combined.
Form the mixture into small meatballs, about 1 inch in diameter, and set them aside.
Heat a skillet over medium heat and brown the meatballs on all sides, about 5-7 minutes. Transfer the browned meatballs to a baking dish.
Pour the marinara sauce evenly over the meatballs in the baking dish.
Sprinkle the shredded mozzarella cheese on top of the sauce and meatballs.
Bake in the preheated oven for 20-25 minutes, or until the cheese is bubbly and golden brown.
After removing from the oven, let the casserole sit for 5 minutes. Garnish with fresh basil before serving.