In a bowl, mix flour and salt. Pour in water and mix with a spoon until the dough comes together. Cover with plastic wrap and let rest for 5 minutes. Remove dough from bowl and knead for about 5 minutes moistening your hands and the board with water as you work. (Kneading in the additional moisture is an important step in making a tender arepa.) The dough should be smooth and not crack around the edges; it should be moist but not sticky. Form into disks about 3-inches around and 1/2-inch thick. (The disks can be wrapped tightly in plastic wrap at this point and cooked later.) Add the oil to a non-stick pan over medium heat and cook arepas on each side just until a crust forms. Do not let brown. Place on an ungreased baking sheet and bake for 15 to 20 minutes or until the arepas make a hollow sound when tapped. Open a slit in 1 side of the arepa to make a pocket (or slice in half). Arepas can be stuffed with meat, beans and plantains or your favorite filling.
Arepa flour is a precooked corn flour and should not be confused with masa harina. Arepa flour is sold as masarepa, harina precocida, or masa al instante. It can be found in Latin American groceries.