But it challenged me at every turn.
My biggest mistake was trying to get away with a thin back plate for the large stone.
Then I realised it was too thin and I remade the whole of the top piece using .8mm back plate which was probably too thick for my torch to handle. Then when I was setting the stone the whole thing came off the ring. AAGH. luckily I was able to remove the stone without too much damage and resolder it to the ring. I made sure it was soldered properly this time!