My driveway is half-sloped...meaning the camper and the jacks for it are more or less on a flat section. The rear tires are, of course on the flat section, but the front tires are on the sloped section. I drive in backwards and then put my small leveling ramps I use out in the boonies behind the front tires and then carefully back up on them. My "ramps" are made from 3/4" plywood with one 2" x 6" full length with a 45 degree cut on the front end to drive up on. I have a second 2" x 6" with a 45 degree end that is attached to the other 2" x 6" which lets me back up even further to get the FRONT of the truck up the total height of the ramps (3/4" ply plus two 2" x 6"s).
That levels the camper to where the jacks are located and it is simple enough now to raise the camper and drive forward out from under the camper on the jacks.
HOWEVER: I have to raise the camper enough to allow for the truck bed to clear the front of the camper as I start down the sloped section as it is now lighter and will sit higher at the rear of the truck bed.
NOTE: It is never a good idea to leave your camper on the jacks for the winter or even for any length of time. Lower it onto a framework of cribbing that distributes the weigh on many cross members! You can choose to leave a LITTLE upward force on the jacks but for any length of time, why not get them indoors for the winter also.