From the Boundary Trailhead, hike the road for a half-mile to where French Creek intersects with the Boundary Trail. Cross the ridge-top Boundary Trail and continue down the other side into the head of French Creek. There are no signs for the French Creek Trail.
The true trail starts in about 0.25 miles past the junction with the Boundary Trail, when it drops down into a recovering clearcut, then eventually into virgin forest. This is where the big trees begin. One after another, huge, ancient trees on both sides of the trail.
The French Creek Trail was built by the Sierra Club a few years ago and is in good shape. Although it is designated only for hikers, horses and mountain bikes, motorcycle riders use it and various crews perform maintenance on the trail to keep it hikeable.
After about 2 miles, the trail flattens out and there is a nice campsite next to French Creek. A mile past this, the trail continues another mile to the junction with the Quartz Creek Trail. This intersection is unsigned but obvious.
It is possible to loop back to the trailhead using Quartz Creek, but the way is more rugged and damaged by ORV use.