It is hard to degraft Ariocarpus fissuratus.
When you cut a part of fissuratus during a normal degrafting, liquid came out from the body and is hard to stop.
One of possible degrafting method is remaining vascular bundle of the grafting stock.
This method is not necessary to cut a part of the body.
The photo is A. fissuratus f Big Bend, degrafted with the vascular bundle years ago.
I assume the vascular bundle has died and roots have come out from the body.