Southside is an alternate route to and from the summit of Lazy Mountain. It is less steep than the main trail, but steeper than the Lazy Moose Trail. The route connects with the Matanuska Peak Trail, which originates at the McRoberts Creek Trailhead.

Lazy Mountain Southside is the descent portion of the Crazy Lazy race course,  a race held in March which climbs Lazy Mountain beginning at the Lazy Mountain Trailhead, then descends down Lazy Mountain Southside to the Matanuska Peak Trail, and finally loops back to the Lazy Mountain Trailhead via the Morgan Horse Trail.