Put a service in a room and a booking holds that room against everyone else — other practitioners and classes alike. Without a room, each practitioner's calendar is checked alone.
Prerequisites
Rooms → Manage Rooms → + Add room. Name it the way your team says it out loud ("Practitioner Room"). Leave "Allow concurrent bookings" OFF — that setting is for offsite or virtual spaces where several things genuinely happen at once, and a room with it on is never held.
Appointments → Appointment Types → Edit → Room. Every service held in that space points at the same room — Reiki, sound healing and massage in one treatment room all pick that one room. Services that tie up no space (home visits, anything offsite) stay on "No room".
Book one practitioner for, say, 2:00 PM. Open the booking page for a second practitioner who offers a service in the same room on the same day: 2:00 PM is gone from their times too. Classes held in that room disappear the same way.
The room is checked in both directions: a 1-on-1 booking blocks a class being scheduled into that room at the same time, and a class in the room removes those times from every practitioner who works there.
The service's buffer time counts as part of the room's occupied stretch, so turnover between two practitioners is respected the same way it is for one.