At its centre is a distinct hollow, and curving around that hollow to the north and south are two pronounced arms of raised earth. This is a fulacht fia, a type of prehistoric cooking site found in considerable numbers across Ireland, typically in wet or marshy ground close to a water source. The general principle involved heating stones in a fire, dropping them into a water-filled trough to bring it to the boil, and using that heated water to cook meat. Over repeated use, the shattered, heat-cracked stones were raked out and piled around the trough, gradually building up the characteristic horseshoe or kidney shape that survives in the landscape today.

At Lissatava, the evidence of that process is still readable in the mound itself. Where farm stock have eroded the edges, fragments of heat-shattered sandstone sit in charcoal-rich soil, the direct residue of prehistoric fires and boiling. The central depression, roughly two and a half metres north to south and three and a half metres east to west, likely marks the position of the original trough. The mound is lowest on its western side, and a small pool of standing water was noted immediately to the north at the time of survey, possibly a recent digging-out but in any case occupying ground that would naturally have held water. A second burnt mound, a closely related site, lies approximately thirty metres to the south-west, suggesting that this wet patch of ground was returned to, or used in parallel, at some point in prehistory. Two smaller depressions on the mound's surface, one on the north-north-west edge and one on the south side, add further texture to a site that has clearly been subject to both ancient activity and more recent disturbance.