Hi Nikki,
Yup, i booked all my consult appointments beforehand. It's best to book before your trip to Korea, especially if you are short on time, so you don't waste time waiting in queue to see the doctor if you do a walk-in consult. Plus, there's no guarantee you can consult with the doctor of your choice, or even getting a chance to consult (especially during peak PS seasons or for certain clinics where you meed to book months in advance) if you do a walk-in.
For Naturalism, i had to get the help of my translator after I hired her service, to book an appointment with the clinic, as I was having difficulties communicating with the clinic to book a consultation slot via kakao due to the language barrier.