To make this oblique cut, you will need to use a sliding taper cutter on a table saw. They are actually quite easy to make or you can buy one (I think Sears carries them...but certainly a local Delta dealer will have them). There are several carpenty and cabinet makers books in the library that will show you how to build one.
Trying to do this on a jointer will be very difficult. You will have to elevate the back trailing edge to a certain height (this will be a guess) using a big space block, I suppose, and then run the piece through over and over and over, until you whittle it down. Nah.....use the sliding taper cutter.