We've instructed users to set their status to Do not Disturb when they get up from their desks (i.e. lunch, restroom, etc.). That way the system won't consider them available in a queue and other internal users won't try to call them as they're "red".
They just need to open their RingCentral Phone application, click the dot/number on the upper left, and then click "Do not Disturb". They can also click the pencil icon under their name to write a message (i.e. "Lunch") so that other users in the HUD know where they are.
Users just need to remember to click "Available" when they return. If they do set a message/status, they'd need to clear that as well (click the pencil and then click the little x).
If your users have scheduled lunches, you
could set up Custom Rules for that hour or so in the users' Call Handling settings, but we find the Do not Disturb method works fine.
DND takes some getting used to as users will forget to switch their status (both to DND and back to available), but someone in the office will end up reminding them.