According to my map it's 260 North East from Payson. About 12 / 15 miles along 260 you should hit the FR300, Turn West onto FR300. Then another 10 or so miles along FR300 (Past Woods Canyon Lake & Bear Lake) you hit FR295E which heads up to Knoll lake.

If I'm wrong please correct me someone.

http://www.fs.fed.us/r3/coconino/recreation/mog_rim/knoll_camp.shtml

Or from that map it seems you could take Hwy87 North from Payson, then hit the West side of FR300 and take that right accross. I'm thinking I might head home that way on Sunday, so we get to see the views without being in a rush to get somewhere before dark. Plus I want to check out Kehl Springs campground on the West side of FR300 as that's a free camp ground. If that looks nice then I'll head there sometime in the future.