The principle was simple enough: stones were heated in a fire, then dropped into a water-filled trough to bring it rapidly to a boil. Over time, the repeatedly cracked and discarded stones accumulated into the characteristic horseshoe-shaped mound of scorched, shattered rock that survives at many such sites. At Barryscourt, the spread runs approximately six metres north to south and the same distance east to west, a modest but legible footprint in the ploughed ground.

What makes this particular site quietly telling is its relationship to a landscape that has since been substantially altered. A stream once ran adjacent to the site, recorded on the Ordnance Survey six-inch map of 1935, but that watercourse has since been drained away. The presence of a stream was not incidental to a fulacht fia; it was essentially the point, since a reliable water supply was necessary for the whole process to function. Its disappearance is a small reminder of how thoroughly post-medieval land improvement and drainage schemes reshaped the Irish countryside, erasing the hydrological features that prehistoric communities had specifically sought out. Two further fulachta fiadh lie in the same field, suggesting this area was returned to repeatedly, possibly over a long period, by people who valued this particular combination of water, fuel, and open ground.