These ancient cooking sites, found in their thousands across Ireland, typically date from the Bronze Age, somewhere between 1500 and 500 BC, and they follow a remarkably consistent pattern. A trough, often timber-lined, was dug into the ground and filled with water. Stones were heated in a nearby fire and dropped into the trough until the water boiled, and meat was then cooked in the steaming water. The burnt and shattered stones, discarded after use, accumulated into the characteristic mound that survives in the ground today.

The sheer number of these sites across the country, well over four thousand recorded examples, points to how deeply embedded this method of cooking was in everyday Bronze Age life. Mayo, with its boggy ground and abundant stone, was well suited to the practice; the waterlogged soil that makes farmland difficult to drain also helped preserve organic material and the subtle earthworks of ancient activity. The place name Lack itself likely derives from the Irish leac, meaning a flat stone or flagstone, which fits comfortably in a landscape where stone was a constant presence in daily life and in ritual.