What bow?
I assume it doesn't have a shelf of any sort so they'll be shooting off the hand?
Are they going to use a shooting glove? If they are, then the nock point can be pretty much the same as when shooting with a shelf.
If not, it's perfectly easy to lift the nocking point a touch so that the fletchings* clear the skin of the bowhand easily.
My nock point is (IIRC) 1 arrow nock's width above where it would be if the arrow was 'flat'. (if that makes sense!)
I get this position by suspending the bow so the string is horizontal, then suspending an arrow from the string (vertically) until it's laying against the bow at the desired arrow-pass-position. I then make the move the arrow 1 nock's width 'up' the string, and that's my nock point.
Currently I'm using plastic nocks on my spruce shafts (not sure which nock tbh).
You do loose a little distance (the arrow will be higher on the string, thus pointing 'down' a bit more), but the speed of a horsebow tends to help regain it.
oh - for reference I shoot 1 over, 2 under, (Mediterranean?) and field draw (to the side of my face) rather than to under my chin.
* I'd NOT shoot with plastic vanes off the hand!