It measures roughly eleven metres north to south and eight metres east to west, rising only about thirty centimetres above the surrounding ground. At its centre is a shallow depression, just over a metre and a half across. To most eyes it would read as a slight unevenness in a wet field. In fact it is a fulacht fia, a type of prehistoric cooking site found in their thousands across Ireland, typically dating to the Bronze Age.

A fulacht fia, in its most common interpretation, functioned as an outdoor boiling pit. Animal hides or troughs were filled with water, and stones heated in a nearby fire were dropped in to bring the water to a boil. The shattered, fire-cracked stones were then discarded to the sides, building up over time into the characteristic horseshoe-shaped mound of blackened debris that survives to this day. The dark soil and fractured stone that make up this mound at Bracklaghboy are precisely that accumulated residue. The site sits at the edge of a broad, low-lying sweep of flat, damp ground along the southern bank of the Mannin River, with rising ground beginning about thirty metres to the south. The waterlogged character of the land would have been a practical asset rather than a drawback, providing ready access to the water essential for the process. Two further examples lie roughly a hundred metres to the west, suggesting that this stretch of riverbank saw repeated or prolonged use over time, though the mound itself is poorly preserved with an uneven surface.