This is more a question for mathematics academia, but may apply more broadly.
I have left academia long ago, but there are a few problems and conjectures, not especially famous but that I find really interesting, that I would like to see solved. Nobody seems to be really working on them, at least in the past 10 years.
I am considering either putting up a prize or hiring talented folks to work on them.
What's the best way to proceed : where to advertise for that? Or should I just email some experts or grad students whose research records hints they might make headway if they accept? Or organise a sort of workshop and invite folks (with some contraint that what has been tried or found be written up)?