Mix the cornmeal, water and salt. Use your hands like in the video, until the dough is soft... if you feel little balls, keep mixing it and squeeze those balls.
When the dough is ready, grab some and make a ball first, and the pat it until it flattens. Not to flat, it should be 1.5cm thick. Put it on a frying pan or budare. (Put some vegetable oil, and with a napkin you can spread the oil in the fraying pan)
The arepa should be cooked for both sides. Put some cover, it will be like baking your arepa and it will cooked better the inside.
For the filling, mix the shredder onion, shredded chicken, avocado, mayonnaise, salt, and if you like add some pepper in it. Mix like in the video.
When your arepa is ready, open in the middle, put some butter if you like, and add the filling. Enjoy!