While the voting poll is still running (see previous post) I thought I would show how I am currently attaching the pins to the back of my brooches.
I make and bake the front of the brooch first. Then I add a layer to the back of the brooch. Before baking, I cut out the shape around the fastening pin, so that it fits neatly into the recess. I bake the brooch again with the pin in place. When it has cooled, I pull out the pin and then glue it back in place with a two-part epoxy glue.
Having tried various methods, this is my preferred option for a really neat finish. I think gluing the pin into the recess gives a stronger finish than just gluing onto the surface of the brooch.