No access to domino unfortunately. The original had the ‘harp strings’ (another new term learned!) tenoned in, but I accept the point and could easily screw those. Ditto the turned pieces which were also mortised in. The whole thing will be painted with a good few coats and consequently can be filled, sealed etc around any gaps on joints to minimise any water penetrating, but is also no harm and potentially easier to just use fixings.
All this aside, my main quandary is still the joint in the bottom corner and how to connect 4 pieces together. I’ve been playing around with some lap joint ideas based on what toolkit said, but worry it’s getting very elaborate. Maybe not so much as mortise and tenon on 3 sides perhaps…
…really must learn sketch-up