This is a reposted comment from the Mechanical Puzzles Discord. There was a great discussion about design; it’s worth checking out if you’re thinking about designing your own puzzles. We need more makers!
It’s very difficult to get it right and you won’t please everyone, so don’t try.
A puzzle doesn’t have to be hard to be good. In fact I think it’s hard to make a difficult puzzle really good, because of the fine line between aha and what a pain in the ass.
IMO the essence of puzzle boxes is using the solvers assumptions against them.
Unconscious assumptions you can build into joinery and shape. You can also create assumptions and then use those against the solver; this is perhaps my favorite thing.
It’s an art for sure. Try, don’t be afraid of failure, learn and expand your repertoire.