Here is an animation of how it is done: http://www.pemnet.com/design_info/video_library_fh_test.html
I bought some 3/4" round bar made from A2 steel to make the anvils from.
Bottom anvil, top anvil, PEM stud, test piece of sheet metal, and a couple of spacer nuts.
PEM stud seated in the sheet metal on top of the bottom anvil
Just before pressing
PEM fully seated
Completely flush on both sides