From Strawberry on 109, drive east to 5N09 road. After 1 mile take "Hells Half Acre Road" (according to Google Maps), which is right at the fork. After another mile take a left at the fork to 5N06 (not right to 5N15Y). This eventually takes you to 5N09X road. There are informal campsites along here. No toilets, firepits, or cell service. 

Alt description from the Sonora Pass Highway Book:
To reach 5N09X, turn left from Highway 108 onto paved Beardsley Road 1.4 miles east of Herring Creek Road. Exactly one mile from the highway, where the paved road starts to curve left, exit right onto dirt Road 5N95. At 0.2 miles, 5N95 curves sharply to the right. After 2.0 more miles (a total of 3.2 miles from the highway) Road 9N09X leaves 5N95 to the riht. 9N09X extends 8.2 miles from this junction to a gate and fence which stop traffic just before Donnell Reservoir. 9N09X is sometimes called "the 4700 Road" due to it's elevation.

Road names may change over time. I couldn't find Beardsley Road on Google Maps but I think it's the same as 5N09.