Have raised slate tiled floor, need recessed cover say 200mm x 200mm into
which I can put a piece of slate tile so cover is unobtrusive. Where can I
get one? What are they called? Build Center et al websites are grade A
pants. Is needed for access to drain cocks for central heating which then
drain away through pipe under new floor. I have used a full size recessed
cover for an inspection chamber and wish to find a small cover for the
above.

Plus any tips for grouting uneven surfaced slate with mortar mix (this is a
semicovered mini-courtyard)?