Each employee gets a link to book a session online at a time that suits them, during or outside working hours. No forms through HR and no queue. The first session sets out where they stand. After that, they come back whenever something changes: a new baby, a house move, a promotion, a pension statement they do not understand.
What an employee tells their advisor stays between them. If you want a report on take-up, you get overall figures, never personal details.