Near Sedona: Huge free camping area along Forest Rd 525 in the Coconino National Forest, about 25 minutes from Sedona. There were at least 100 RVs, vans and a few tents scattered along this road camping when we were there in April. We camped here. More details on my travel blog.
From Jeff H:
Near Phoenix: Robbins Butte Dispersed BLM site. Stay left at the Y. Crowded toward the near end. Go another mile or so back towards the small hill (washboards) and there are more sites, nice for a night or two. Good scenery. Plenty of old shotgun shells and brass on the ground (33.310967, -112.656135) (from Jeff H)
(32.343052, -112.870767) Just about as gorgeous and quiet as can be. Wide open views, much desert vegetation and beauty
(31.767417, -110.625361) Spectacular spot. Views. Quiet. Stars. Running and riding. Very fast internet. Perfect for a long digital nomad stay.
(33.455792, -113.035084) Spectacular BLM site. Scenery, hiking, great cell reception.