Preheat the oven to 350°F (175°C) and spray the casserole dish with cooking spray or lightly coat it with olive oil.
In a large mixing bowl, combine the cooked and shredded chicken with the marinara sauce and mix well to ensure the chicken is evenly coated.
In a separate bowl, whisk together the almond flour, garlic powder, dried oregano, salt, and black pepper.
In another bowl, beat the two eggs and set aside.
Layer half of the chicken mixture in the bottom of the prepared casserole dish.
Sprinkle half of the mozzarella cheese over the chicken layer, followed by half of the Parmesan cheese.
Pour the remaining chicken mixture on top, spreading it evenly.
Top with the remaining mozzarella and Parmesan cheese.
Drizzle the almond flour mixture evenly over the top, creating a crunchy layer.
Bake in the preheated oven for 30-35 minutes, or until the cheese is bubbly and golden brown.
Remove from the oven and allow to cool slightly before slicing. Garnish with fresh basil if desired, then serve.