Soldering is the technique used to join metal that is melted to fill the open seams and connect the metals.
Step 1: Displayed above, is the solder placed onto the bezel. The next picture shows how the solder is lined up, on the inside, right against the bezel edge.
Step 2: The two pictures shown is step 2 show the torch, heating from below the metal with even heat. This continues for a few seconds, until the soldering flows into the seams.
The final product shows the bezel soldered onto the metal backing piece, with the stone in the bezel.