After ploughing, a dark spread of burnt material surfaces across the field, the only visible sign of a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, particularly in wet or marshy ground.

A fulacht fia, in its simplest form, is a Bronze Age outdoor cooking place, typically consisting of a trough, often timber-lined or stone-lined, filled with water, and a mound of shattered, fire-cracked stones nearby. The method involved heating stones in a fire and dropping them into the water-filled trough to bring it to the boil, then using that heat to cook meat. Over time, the broken and discarded stones built up into a characteristic horseshoe-shaped mound, often a dark, charcoal-rich material that survives well in the archaeological record. The example at Knocks sits in exactly the kind of low-lying, potentially damp ground where these sites are most commonly found, suggesting the original users chose the location deliberately, perhaps for its proximity to water or soft ground suitable for digging a trough. The charred, crumbled stone that emerges after a plough pass is the accumulated debris of that repeated process, preserved in the earth for potentially three thousand years or more.