Line a 9" pie plate with half the crust. Try out the salt pork until crisp. Arrange the salt pork, potatoes, and clams in layers in the pie shell. Add the clam liquor, pork fat, salt, and pepper. Dot with butter. Cover with the top crust and bake at 400 degrees F for 10 minutes, then reduce the heat to 350 degrees F and bake for 20 minutes more.