Montreal is 13 hours behind Seoul

There is no standard 8-to-6 overlap. Someone joins early or late.

Given Montreal is 13 hours behind Seoul, the realistic answer is that there's no convenient shared slot during normal business hours. Catch the edges of the day: the last hour for Seoul or the first hour for Montreal is usually the least painful option. Just remember Montreal changes its clocks for daylight saving and Seoul doesn't, so confirm the overlap whenever the seasons turn.