In a bowl, mix together the cooked and shredded chicken, scallions, white onion, red bell pepper, garlic and cilantro. Set aside.
In a small bowl, whisk together the mayonnaise, lime juice, avocado, hot sauce, salt and pepper to taste. Add to the chicken and mix gently until combined. Refrigerate until ready to serve.
To assemble: Place the arepas on a serving plate, top with the chicken and avocado mixture. Add some avocado on top and sprinkle cilantro or parsley . Serve immediately.