Park at the Coquibus Rumont car park, take Chemin Boulignere then after 100m take Chemin du Bois de la Guichere on the right until you reach the intersection with Chemin des Cent Marches, take the latter on the right on about 50/100m until you cross a path that goes up on the left, take this path for 50m then go up the slope to the left. The boulder is at the top.