exec wants to do open office hours

Hi all, title says it all. Exec wants to start doing open office hours. So far she has decided:

20 min each session

either in person or Teams

For those of you who deal with this, how do you manage? Does the staff reach out to you directly to book a time? Or do you use Calendly?

Also, how do you frame the language to the staff? I want to frame it as "hey, please come talk to me for 20 minutes, but please make sure you come prepared with a topic and it can't be anything too personal or time-sensitive., or personnel related issues".

I'm worried this may back fire and staff will come to her with critical needs. Any idea how to navigate this? Or word the invite correctly?