The list on the board is fine.
Talking to the kids is fine.
Almost any way of doing it is fine if the reflects the personality of the coach and school/organization. It's only wrong when the coach gives off what I can only describe as a phony vibe. Then the kids think the whole tryout process was a nothing more than a dog and pony show and bitterness can linger.
As a coach, I'd prefer the more personless approach and simply post a list. If I felt the need to talk to a particular cut, I'd do it before I posted the list (but I'd try to resist that urge). If a cut wanted to talk to me about it a week or two later, that would be fine. But I would not discuss it until then.
Cuts was tough. The cleaner the break, the better it is for all concerned.