With the aluminum pressed on front to back, fold the aluminum down onto the sides.  You will find that there is an excess of aluminum at the corners.  That's ok.  Just fold it like paper over a package.  We will take care of that later. It will get pressed in tightly or if it gets ugly, then you'll have a model that has been in a minor accident.  Its a JUNK YARD, so don't worry about making it PERFECT!