"Bob Swinney" wrote: (clip)solder next to the rod,
and laying in the flux. You may want to use some sort of a fixture, or
holding device, to make sure the square doesn't move (clip)
^^^^^^^^^^
After you adjust your torch to a neutral flame, just brush the end of the
flame back and forth across the assembled joint, to keep the heat down.
Oxy/acetylene is way overkill for this job. If you have silver solder in
sheet form, you could put a small clip of this between the end of the rod
and the middle of the plate, and then use downward pressure on the rod to
hold everything in place. If you have wire silver solder, hammer the end
flat, and then break it off and proceed as above.

Watch carefully that the edges and corners of the sheet don't overheat.
They can bead up on you very easily while you are waiting for the solder to
melt.