The mound at Clashroe measures roughly five metres east to west and nine metres north to south, rising only about thirty centimetres above the surrounding ground. Its western face opens with a gap just over a metre wide, and the whole structure is composed of burnt material, the characteristic signature of a fulacht fia.

A fulacht fia is essentially a Bronze Age cooking site, though scholars have proposed other uses over the years, including brewing and textile processing. The typical method involved heating stones in a fire, then dropping them into a trough of water to bring it rapidly to the boil. The cracked and spent stones were raked out after each use and piled nearby, and it is precisely this accumulating mound of fire-shattered, heat-reddened stone that survives as the visible monument today. The kidney or horseshoe shape is common to the type, often forming around the trough itself. What makes Clashroe particularly notable is its company: it is one of a cluster of five such monuments in the immediate area, which suggests this stretch of ground beside the stream was returned to repeatedly, perhaps over generations, by people who found the combination of running water and open ground well suited to their purposes. Such groupings are known elsewhere in Ireland and hint at the social or practical significance of particular spots in the prehistoric landscape.