Rare-earth magnets can be difficult to separate when they are stuck together, but here’s a simple jig I use that solves the problem. It’s a scrap of plywood with a shallow hole drilled in it that matches the magnet’s diameter.
I drilled it just deep enough to recess one magnet. A second smaller hole in the middle of the magnet recess goes all the way through the plywood. To use the jig, I place both magnets on top and swipe the top magnet off of the bottom one with my finger. Then, I poke the recessed one out of the jig with a dowel.