Nearly two metres in length, it is carved in false relief, meaning the design appears to rise from the surface even though it is the background stone that has been cut away. At the centre of the composition is a stepped Latin cross with a framed border, its head and arms resolved into a central lozenge terminating in fleur-de-lis motifs. One of those arms carries a triskele, the ancient three-legged spiral motif that crops up across Irish and European decorative traditions. A small roundel sits at the lozenge's heart, and above the cross head the IHS monogram appears, a Christogram derived from the Greek spelling of Jesus, with a small cross rising from the crossbar of the letter H. Latin inscriptions run both beneath the base of the cross and around the framed border of the slab itself.

According to the border inscription, the slab is a memorial to the Madden family and dates to 1648, a year that fell in the turbulent middle of the Confederate Ireland period, when much of the country was caught between competing military and political forces. The Maddens were a Connacht family of some standing, and commissioning a carved memorial slab of this quality, within the chancel of a friary church, speaks to their status and to their relationship with the Dominicans who occupied Portumna Friary. The combination of motifs on the slab, blending the formal Christian symbolism of the IHS monogram with the older decorative language of the triskele and the fleur-de-lis, is typical of Irish ecclesiastical carving in the late medieval and early modern periods, when craftsmen drew freely across a wide visual vocabulary. The relatively plain shaft and base of the cross throw the more elaborate upper sections into sharper focus, suggesting the carver made deliberate compositional choices rather than filling every available surface.