JerryG has got it right...
You can do the same thing with a box blade or just a heavy duty grader blade (which I personally prefer for a variety of reasons).
1) Go to a level surface. I park on the asphalt road in front of my place. Set your blade just above the surface (or right on it) and set your 3pt lock (if you have one) in this position. If you don't have a lock, use a pencil and mark the position.
2) Get out of the tractor and level the blade right to left with your 3pt crank or your hydraulics.
3) Get back in the tractor, lift your 3pt up and go to the site your are trying to level. Drop the 3pt to your mark or lock position, and drive until your done.
Doing it this way, you don't have to mess with your 3pt at all while working with the blade. You'll only cut down the high spots and move them into the low spots. It takes a few passes but you end up with a completely level area pretty quick.
I've used this process to level my wife's riding ring, spread gravel, sand, build roads, driveways, etc... it works great. Note when building a road, make sure the blade is initially set at a right/left angle, so you cut the road in with a peak in the center for drainage to the sides. After a few passes, you'll have your drainage angle and then you can straighten out the blade again.