Fossil Creek
Its pretty rough road getting out to fossil creek. Like 28 miles of washboard. I dont know how nudist friendly fossil is but up over the mountain and down to the verde River is nudist friendly at the verde hot springs. High clearance vehicle preferred.
Please be aware that a reservation system has been established for Fossil Creek because the area was being overloved, so to speak. If I recall correctly, there are 148 permits available each day and can be purchased on-line. Reservations are only required April 1 - October 1,
Link: https://www.fs.usda.gov/detail/coconino/recreation/?cid=stelprd3852090
Verde Hot Springs. There is a campground there once you get to the bottom of the hill at the river. The campground is not nude friendly that I know of. To the north of the campground are the springs. About a 3/4 mile hike up river. It's nude friendly there.