The easiest way to get to this site is by approaching from the south. Take the path with the steps up towards the summit of Blackford Hill, but maybe 30 steps from the top the gorse to your left stops and is replaced with grass on a steep slope. There are a couple of faint tracks visible here. Leave the main path and walk around the edge of the hill towards the prominent tree, where the gorse starts again. Once you reach the tree the hollow in the rock and the carving itself are both clearly visible.
There’s quite a lot of scree and it is steep, so appropriate footwear is required!