The method of construction and fastening of the heel on my sabs is ahistoric. Instead of building a hinge, he just floated the heel/foot interface on a piece of leather. Halberds also used modern (aluminum I think) grommets for the toe pointing holes, and the top opening is too large and not closely fitted to the ankle so they wind up outside the bottom of the greaves. I didn't know enough about sab construction when I ordered them 3 years ago and so when I asked for historically accurate, I just didn't know any better and assumed it was good to go. The general shaping is just a little off too.
They should have a metal hinge construction to attach the heel plate, and then a small leather strap to secure the other side, though some examples seem to use a small hook/clasp assembly on the side opposite the hinge. The top of the sabaton must interface with the greaves and provide seamless coverage between the top of the sab and the bottom of the greave while not impeding movement. The sab should be inside the greave, not the other way around.
They
should look like this: