Cothillock when you see it on the OS or Phillips maps appears to an easy cairn, near the road in a small wood. Nae probs, says me.
Heading east after Arthurhouse on the B967 stop after the Lewis Grassic Gibbon centre at the road end to Pitcharles. The cairn is in the small wood. For me it took ages to find, up and down I looked, crawled and jumped until eventually I flung myself thru a gap in the trees to land on the cairn edge. If I'd approached from the south there is a gap but I didn't spy it, handy for getting out tho.
The cairn is 14 meters wide and just over a meter high. There is damage to the edges with eastern side jumping down at least 3 meters. One or two bits of cairn material can be seen amongst the turf. It is well protected and hidden by the trees. Still if the mist had been here, like at Montgoldrum, it would have been 'well scary'.