No special access issues
Park your car in the kafenio that you find on the road to the top of Ymittos. You can also park further up, in the entrance to the dirt road that goes under the block. From this dirt road, in the first inner "corner" on the road that you come to, is the path to take up to the block. It is a bit of a steep path that follows the mtb-track. Follow this path for around 70 m until you find yourself again on flat ground, like you are on a big shelf in the mountain. You find the hidden block after another 25 m on the path, on the right hand side in the trees. Look for the rocks that are hidden there.