It was still intact: roughly 2.1 metres long, 1.2 metres wide, and 0.6 metres deep, framed with oak slabs along its sides, smaller oak planks making up the floor and one end, and an upright stone flag sealing the other. Around it lay heat-shattered stones and soil blackened with charcoal, the characteristic signature of a fulacht fia.

A fulacht fia is a prehistoric cooking site, the term referring to the horseshoe-shaped mounds of fire-cracked stone that typically mark where they stood. The standard method involved heating stones in a fire and dropping them into a water-filled trough until the water boiled, food wrapped in straw or hides then submerged to cook. The Coom example is notable precisely because the wooden trough itself survived, preserved by the waterlogged, oxygen-poor conditions of the boggy ground. One detail from the discovery adds a quiet human note: half of a burnt plank was found tucked behind an intact one on the side of the trough, suggesting the structure had been patched or repaired during its working life. The surrounding burnt material was spread across the fields during land reclamation works, and further pieces of wooden planking turned up in the process, though these were not retained. That dispersal makes the original find, documented in the 1930s, all the more significant as a record.