Found this description online:
This is locally known as the "slashing road" section of the North Country Trail, and is an absolutely awesome section. Locals generally ride from the South to the North and avoid much of the sandy two-track. Starting at the intersection of Thumb Lake & Slashing road, take the trail north following the blue blazes on the trees (re-marked spring 2009, very easy to follow) after several miles of flowy single track, cross chandler hill rd. (paved) and then begin a grinding uphill on a fairly decent two-track. At the top of this climb is a real treat if you know what to look for...on the right side is a faintly visible single track that has been built and maintained by a local guy who lives nearby. This "bootleg" section is not marked, but generally easy to follow and forms a 5 mile loop that re-connects with the NTC about a mile from your point of origin. This makes for an awesome 11 miles of riding on mostly single track, while eliminating all of the sandy two-tracks and paved roads in the trails.com description. The soils here drain well, so this is a good choice when other trails are too muddy to ride. First timers should take a good topo map and a compass or gps, since the area is criss-crossed with old logging roads and it can be easy to get lost if you get off-track.
There are other sections of the North Country Trail, but I haven't ridden them yet. Directions are available on Latitude 45's website (Petoskey bike shop). I've been unable to find any descriptions online.