as this is a very simple single glazed system, it was measured and built on site, metal frames are fixed through anchors installed in predrilled holes in stone, glass is just measured on site and cut and stone was ground down to achieve relatively straight lines, without having to fit the glass around. It’s a nice detail, but not particularly challenging. For dimmer a cable is installed in a groove cut in the stone with as simple tools as angle grinder. On a second thought it may even be that smaller stone pieces are stuck along glass edge to disguise the actual sealant/joint and then joint masked with the same grout used around dimmer switch.
