This site is more interesting than Hafod y Garreg but that's not saying much! However there is a clear row of stones on the north-west side that have been set upright and which leads to a cairn to the south-west.
The description in the visit report from RCAHMW is useful: "It comprises approx. 120 small stones set into the turf and aligned generally in rows N.E.-S.W. incompletely covering an area of about 20 M. square. The N.W. most row of stones seems to point towards a mutilated cairn c. 8 M. to the S.W. The stones occur singly and are in every case but one, a boulder 0.6 M. by 0.4 M. and 0.9 M. high, of a generally uniform size. Distances between the stones vary between 0.5 M. and 1.8 M. A clear pattern of regularity is deiscernible although the pattern is incomplete and obscured by turf."