Square shaped rings are tough to size, so this had to be made to order in the customers finger size. We carved a wax of the inner round band and the outer square band and cast them in 14k yellow and white gold. They were cleaned up and soldered together on a charcoal block. I like the hard surface soldering blocks for general soldering. But I like to use charcoal blocks for getting large pieces hot enough for the solder to flow every where it needs to go. As a side note: I also like to anneal metal on a charcoal block. It seems to reflect back the heat to the metal for an even heat.
I had the gold tubes sitting around from a stone bezel ring project. I did not make the tubing myself. I am not that old school that I feel I have to fabricate everything.