I'm guessing that they are fairly simple "claw" rings, used to enhance the gloves without needing to actually attach anything to the gloves (although it does look like the gloves were sewn to give them points too).
There's an interview with Christopher Lloyd talking about his role as Kruge here:
Catching Up with The Search for Spock's Christopher Lloyd
And there's a fairly large image of him with his hands around Kirk's neck that, though not super high-res, might be enough to give you a good idea of how to replicate them:
https://images.prismic.io/star-trek...0ZmM3LWFkNjQtZWNkZTVjODA2MWE5_tsfshd1442.jpeg
Just looking at it, I'm pretty sure that the rings are all more or less the same, only scaled to suit the finger in question (the pinky rings are definitely smaller claws).
There are some more fairly high-quality pictures at IMDB, here:
Star Trek III: The Search for Spock (1984) - Christopher Lloyd as Kruge - IMDb and I think that this one:
Star Trek III: The Search for Spock (1984) -- is a slightly differently-timed shot of the "choking Kirk" scene that I think is good reference too.
I hope this helps!