Our place is in West Bay hence why I left from there, but the route from that direction is also much more pleasant and is almost entirely on trail. The Mountain rd. trailhead is somewhat hidden at the end of a driveway right where West Bay rd. turns.
I have been on the trail from Gambier Lake to West bay, it is now my preferred route as it is more direct for me and also more pleasant as it avoids any active logging and the clearcuts. Also, i took the main route to the lake about 2 months ago, it was in very rough shape, many trees down and that last section that drops to the lake is completely washed out. Its probably the worst i've ever seen it.
here's my Strava route for the West Bay to Gambier lake trail