How do you solder on prongs for half drilled pearls
Usually half-drilled pearls are cemented onto a post.
I find that drilling a hole, even partway through the metal, gives the wire stability to stay upright and not move. If the backside of the piece is unlikely to be on display, it is much easier to drill completely through and place the solder on the back, heating from the front to pull the solder through the hole. You can then cut and file off the excess wire on the back side and trim the ‘prong’ to the length you need.