Some should be sold to fund poaching prevention.
Others should given to artists and civil society advocates who would be given it under the condition that it should be used to create art and artifacts designed to raise awareness of and empathy for precious creatures.
But selling ivory creates a demand for it, and how do you differentiate legal ivory from illegal ivory? And even if you manage to create a system that would allow you to track legal ivory from illegal ivory, which I doubt you could after all the any system can be beaten, all you're really doing is driving up the price. So by allowing any of the ivory to be sold, you'd be endorsing poaching.
Use markers as is done with conflict diamonds.
People are not robots who want more of something after they buy it because a demand is out there. This is silly.
Allowing ivory to be sold makes the sacrifice of the animal not in vain.
Poachers will poach no matter what, even without ivory. Enforcement has to be done either way.
And yet you can buy conflict diamonds with little or no problem. See that's the problem is diamonds don't come out of the ground marked, someone marks them, so move the diamond to a country that is allowed to mark the diamond, and surprise it's no longer a conflict diamond, it has the right marks, so the demand is still there, the groups selling conflict diamonds are still selling diamonds. If you really want to stop conflict diamonds, you ban the sale of diamonds, like they do with ivory. Ivory can only be sold IF you have documentation that it's over 100 years old, there is a tiny exception but that exception doesn't cover elephant ivory.
So if you want to stop poaching, you must stop ALL sales of Ivory, then there can be no exceptions, and I would go as far to say old Ivory must be destroyed, so that you can't own any ivory.