Place the small dome of one side in the hole in the solder brick, making sure that the bead sits evenly. If it is not even, the bead halves can slide apart during the heating process. A titanium, or even a stainless steel wire, can be placed through the bead and into the brick if desired, but avoiding the solder.
Pro Tip: It is very difficult to see the solder flow if there is a good fit between the halves. Since this edge will be filed and sanded, let a bit of the solder hang outside the bead. That way, when the solder flows, you will know it.