Here's some of my nocks I've been playing around with so far.
The method of attachment reminded me of an unusual method, perhaps Persian, of nocking an arrow described in an old book.
They fitted the string with a sort of bead with a cone shaped plug that fit into a hole drilled in the base of the arrow.
A round bead with a concave mating surface was also used.
Theory is this made their spent arrows practically unuseable by an enemy.
Of course one might still fire these arrows using a pinch draw of the type used by some Native Americans who used nockless arrows.
Either way a pinch grip of some sort would be necessary to maintain control of the arrow while drawing.