In the Iron Man 2 movie, the angle of the transform scene prevented me from determining if Tony stepped into a part of the suit, thereby giving the leg and boot armour pieces some sort of guidance down his leg. However, after considering many methods, I determined this was the only reliable way for my suit to work.
So, the toe of the boot and behind the heel are both solid structures, but the "walls" and tongue of the boot both fold into place as I stand up. Essentially, I've created a pair of pants that expand as I stand up, and cling to the black spandex underneath.
I used red bristol board to determine the required shapes of the armour needed to cover the boot.