Add the water and salt (optional) to a large bowl.
Slowly mix in the masarepa and about ½ cup at a time. Using your hands, knead the masa unit a smooth dough is formed. If you find the masa to be too dry and crumbly add ¼ cup of water. If you see your dough is too mushy, add more masarepa. Cover with a kitchen towel and allow to rest for 10 minutes.
Form balls the size of a medium onion and place them between 2 sheets of plastic wrap. Flatten with a rolling pin to your desired thickness.
Using a dessert plate or soup bowl (about 6-7 inches in diameter), cut the dough into circles through the plastic wrap. Remove excess dough and use it to make more arepas.
Set your stovetop to medium and place your arepa on your arepa grill. Cook for about two minutes on each side or until cooked and lightly toasted.
Once cooked, eat as is or store in an airtight container in the refrigerator for upto a week.