Driving along the B836 you will come to a horseshoe bend at the head of Loch Scriven. At this point (next to a bridge going over the burn) is a track north leading to a farm. The stones are easily seen in the field on your right, near the farm house.
You can access the field to the stones via a gate. The field was full of sheep and cows on my visit. As well as views down towards the loch the stones are surrounded on 3 sides by hills. It reminded me of being in Killmartin Glen - reason enough to visit these stones when passing on your way to catch the ferry to Bute.