as of Aug. 2020 - 6 campsites, first come first served. there are two outhouses, trash cans, and a water pump (though I brought my own and can't vouch for how clean the water from the pump is).
it cost $8/night for one vehicle, and required a pass that I didn't have. US Forest Service something, but not Discover.
I found Pine Flats beautiful and quiet. campsite #1, where I stayed, is the only site with its own private access to the river. I enjoyed this immensely.
though it has just 6 campsites, during my stay only half were filled. I think it's far enough from Leavenworth and Chelan that it attracts a quieter type.
I felt more relaxed here than I have in quite awhile.