First, preheat the oven to 400 degrees.
Second, place the dry ingredients: self-rising flour and salt in a large bowl and make a well (or a hole) in the center of the flour in the bowl.
Third, pour the milk into the well in the middle of the flour mixture.
Next, place the vegetable shortening (or butter) in the well with the milk.
Then, using your hands, squish the vegetable shortening (or butter) and the milk together until combined. Some people use a pastry cutter, but I don’t find it necessary. You can achieve the same effect with your fingers—it gets messier.
Slowly mix the milk mixture into the flour by pulling it from the sides of the bowl.
Pour a tablespoon of vegetable oil into a cast iron skillet and use a paper towel to rub it all over the skillet.
When the flour is completely incorporated, separate the biscuit dough into six equal portions.
Roll the dough into a ball. (The dough will be a bit sticky, so you can use a little flour on your hands to keep it from sticking.) You could also use a biscuit cutter to make them uniform in shape and size, but I prefer the homemade, rugged look.
Then, place the six biscuits into the greased cast iron skillet and pat down slightly.
Next, brush with melted butter.
Place the biscuits in the oven for 20 minutes.
Turn on the broiler after 20 minutes and let the biscuits' tops get golden brown.
Finally, pull the biscuits out of the oven and set aside.