No special access issues
Park at any of the parkings on the southern side of Playa Los Alemanes -- boulder is visible from the southern end of the beach (on the side of the lighthouse), and accessible via a trail leading up from the beach. There is also a trail coming down to the boulder from the top (if already up at the lighthouse), but at the time of writing (Dec 2021) this was a bit overgrown and harder to find.