Ride out the 24-Hours of Moab trail from Highway 191. When you approach the Fins at the edge of the Wilderness Study Area the road bends left, to the west. Follow the road through three rocky, technical sections in three washes. Climbing out of the last of these, the road becomes sandy and you'll see a left turn with an area trail sign.
If you decide you want to skip the next very technical sections (the High Dive and Upchuck) and lengthy sandy stretches on the way to Prostitute Butte, you can use this connector to detour back to the Behind the Rocks Road
. The trail is sand and rocky ledges, but since it runs downhill, it's basically a coast all the way. I wouldn't try to ride up it, however.
Near the end, you'll cross a major wash to reach the road. Don't detour down this wash, which is a marked OHV trail: it's a desperate sand pit the whole way!