On the B953 Balbeggie to Abernyte Road, close by the Bandirran Circles and 4-poster. Pass Tullach Ard heading East, until you see a metal gate at the edge of the wood south of the road. Park here, cross the road to the north side and head east approximately 25 paces. And there it is. Not much to look at!
From Canmore: "Traditionally the grave of a suicide, or perhaps the victim of a murder; according to Hunter, that of Macbeth. This grave is marked by a stone slab, 0.5m wide and 1.8m long, lying flush with the ground on the grass-verge of the road and with the modern stone dyke over-riding one end. This stone is probably a 'grave slab' and not a "standing stone" which has toppled over." Whoever the stone commemorates, what a setting, though - Black Hill and King's Seat just to the north - MacBeth has long been linked with this area. There is an ancient hillfort on Dunsinane Hill just to the west, and the OS shows a broch on a subsidiary top of King's Seat. I haven't visited that yet, but shall at some point in the future.