I find this to be a nice alternative to the AZ trail for this 2 mile section. It is much less hilly and loose, and follows a picturesque wide canyon. It is easy to rejoin the AZ trail in the middle or near either end of this segment to make a loop or detour.
From the north end -- At the pond where the AZ trail starts, head East on a dirt road rather than south on the AZ trail. You'll follow the Rio de Flag (usually dry) around a bend and head south. Shortly after heading south you'll come to a fork. Keep right, on the West side of the canyon.
Continue along the canyon past some grazing lands. The two track here has a very singletrack feel to it, although for the most part there are actually two paths.
Continue past an obvious right turn headed towards the AZ trail and you'll veer East for a brief while until you hit a right turn that is marked by branches along the ground. This will head south for a brief while on singletrack until you go through a gate in the fence. This is the junction of the Loop Trail - Walnut Canyon Segment
and the Fence Trail