We focus on developed campgrounds. Dispersed campsites are, by their very nature, hard to pinpoint. You just go, find a spot you like, pitch your tent and enjoy. Some forests are designating dispersed sites but not in Arkansas. Generally, the rules are the same across the country. Take a look at this article http://www.forestcamping.com/dow/suzi/articles/around/dispersed-cg-guidelines.htm
for some general guidelines.
I would suggest you give the Ouachita NF a call just to be sure there aren't any restrictions for the area you want to enjoy and to let them know where you are going to be, in case of an emergency like wildfire or flood.
Happy camping, Suzi