Sedona is not a county seat, so not as much legal business there as in Flagstaff. That said, there are a fair number of lawyers in Flagstaff already-- not sure the population needs a lot more, especially in this economy-- firms are not expanding, and hanging out a shingle is risky.
As for Phoenix, there's more opportunity here based on economies of scale, but things are still pretty slow. Not sure what sort of law you have experience in and will be looking for. I've not been in private practice for a LONG time. Check the advertisements in the state bar magazine, here's the link to the current ones :
http://www.myazbar.org/AZAttorney/cl...NS%20AVAILABLE
I would say the same to you as I say to those in other fields-- have a job lined up, or a big financial cushion, before you actually move here.