I visited this site back in 2008.
Quite a tricky one to find this one. Take the road south from Pontlottyn and drive through Fochriw. Just as approach the cemetary there is a sharp turning to the right. Park near this junction. Make your way up the steep bank and head for the furthest point north. The cairn is not visible until you are pretty much on top of it. From what I remember there is a post stuck right next to the cairn. The cairn itself is of a reasonable size with stones protuding out of the grass.
Not a lot to see for the effort it takes to find it i’m afraid to say.