Upvote:1
You should use e.g. google maps (satellite view). Such things are usually not near (linking) roads, so it is difficult to spot them from a car. E.g. check south west of Falaise.
You should ask to tourism offices about where to find the best "chemin creux" (you can google it, maybe with "carte normandie": you find some circular paths which pass also on the sunken lanes).