Rocher de Milly
One of the furthest approaches in Fontainebleau, but then again, not a hard one. A straight road of about 2km will take you to the area. Also easy to approach with the help of a bike.
The area only features high class problems and a lot of rocks that has or has not been climbed, maybe a good place to hunt for some quality first ascents.
Without GPS coordinates, finding the boulder would be hard. So download the guide and find want you want without problems. It's usually the easiest to stick to the bigger paths for longer walks in-between the rocks.