You can find a couple of places to boondock on House Rock Valley Road. There is also a campground (state Line I think). There is also a campground near the Ranger Station. I saw spots at the Paria Movie set area (very beautiful area) and someone was camping there but I am unsure if boondocking or paid.
It all depends on what you are driving/towing, what the weather is like or going to be, and how confident you are in your skill set as to whether you can get to some of these locations. Beautiful area though. We did end up spending some time in Wahweap camping on Lake Powell if you need full hookups. They were pretty nice and most has a great view.