Hike in eastern Zion Park - to the base of East Temple.
For those in the know: drive through the tunnel, park on the right at the top and walk left to the
Canyon Overlook (20min). There turn right and walk up the steep
up the mountain. There is no path there.
At the top you come to the base of the huge boulder, East Temple.
After the ascent to the saddle descend to the right of the East Temple on the other side
and through various canyons Canyons and the dry wash back to the road.
There through the tunnel, then keep right to Slot Canyon.
In total a good 6 km and about 420 vertical meters.
Without GPS it is completely impossible to find through the maze of canyons!

GPS data for this:

Entrance on the road just after the tunnel:  N37°12'48,3" - W112°56'26,4"
Viewpoint, end of the trail: N37°12'47,7" - W112°56'44,0"
top 1: N37°13'04,1" - W112°56'41,4"
up 2: N37°13'08,5" - W112°46'46,9"
down intermediate point 1: N37°13'15,5" - W112°56'30,8"
down intermediate point 2: N37°13'17,5" - W112°56'17,4"
-- then descend into the lower wash canyon and follow it to the right until you reach the road.
The road is reached at:  N37°12'55.5" - W112°56'08.7"
We now either go back on the road to the parking lot,
or cross the tunnel and follow the Wash downhill to the parking lot,
which is the nicer way, because you still pass through the slot canyon!
All in all a very excellent tour with great views - and you don't meet anybody!

All pictures have the GPS data in the Exif.