After sawing the 45 degree angle, I double checked it. 
Then I set up the jointer and gauge fence for clean up. 
The fence helped keep the angle as I cleaned off the saw marks. 
Then I did a final localized clean up with my block plane. 
After I cleaned up, I double check the angle again. 
Then I used my small router to create a mortise for the hinges. 
One side of the hinge done.
Above is the process I used to create the fold down drawer front for the pull out key board tray. The drawer front is not yet cut to size so it will be significantly smaller.