From the top of Teton Pass, take the service road to the south. At the top of the service road, continue south on the singletrack. This is a casual ~1.8mi climb toward Blacks Canyon trail. Look for the well marked Lithium trail sign in the woods on the left.
Descend the first mile of high-speed singletrack until a short but steep hike a bike. The next mile is an extremely rocky and steep ridge with high consequences for crashing. Dont be too proud to get off and walk your bike. A rescue is a few hours away at best so use good judgement and ride within your ability.
Eventually, the trail turns north and away from the ridge. The singletrack flattens somewhat and speeds along through the forest until it intersects with Big Rocks Trail. Slow down and watch out for horses and hikers as you cross over to lower Lithium Trails jump section. Most of the jumps have gaps and all have ride around options. Lithium Trail ends by intersecting with the very end of Black Canyon
Trail. Turn left, cross the bridge and meadow immediately after. Finally climb a short distance to the parking lot at the bottom of Old Pass Road