I agree that this is pretty difficult to find. We would have had no chance at all if we hadn't asked at the 'Tea and Books' store in Dervaig. A cheap local guide is available giving accurate directions to the site and others. The path here is extremely boggy, and watch out for ticks, as we all came back with quite a few. However it is worth visiting and makes a good compliment to the other two Dervaig sites.
I thought I would cut through the forest to find these stones which was not a good idea. I was relieved to have my GPS in the rucksac which let me find the site and get back to the car via the path I should have followed in the first place. Caught a glimpse of a wild-cat too. Good views from the rocky knoll above the forest clearing which houses the stones.