Epoxy will do nicely. Just enough to wet the bottom and fill up the sides. Practice putting the magnets in dry several times and do not let them smash into each other. I put a mark on one end of each magnet so I can remember what way I want them to go in. Then rough up the sides a little in just a couple places so the epoxy has something to grab. I just took the moto tool and cut two shallow slots is the sides. Nothing that you can see after assembly.
Once in the holes with the wet epoxy, the magnets will stay put till they harden.
Cheers
Dave
