Rather than a single gallery leading to a ceremonial court, this monument contains two galleries arranged back to back, their entrances facing away from each other in opposite directions. This doubled arrangement, with roughly 1.75 metres of cairn material separating the two burial chambers, is a variant of the court tomb tradition, a monument type in which a roofless forecourt of upright stones, known as orthostats, funnels the living toward a covered burial gallery within a long cairn. The Flaskagh More example belongs to a class sometimes called a central-court or divided-court tomb, where two such galleries share a single cairn.

The cairn itself, which runs roughly east to west and measures approximately 22 metres in that direction and 15 metres across, has an uncertain outline, its edges softened by millennia of weathering and disturbance. The eastern gallery is the better preserved of the two, running 6.7 metres in length and divided into two chambers, with a short ante-chamber at its entrance. Traces of a court survive in front of it and slightly to the south, though only two orthostats remain to mark what was once a more elaborate semicircular forecourt. The western gallery is in considerably poorer condition; only its eastern end survives, extending about 2.5 metres, and there is no surviving evidence of a court at that end of the monument. The structural detail was documented by Ruaidhrí de Valera and Seán Ó Nualláin, whose survey of megalithic tombs across Ireland in the early 1970s brought systematic attention to monuments like this one, many of which had received little scholarly notice before.