How to cut a slot at an angle to the surface

[slipstick]

I have a part that needs a slot cut in it at a 12 degree angle. How do I do that? I have a perpendicular slot in the part that is attached, but I need the angle. The image shows the direction.

 

[DavidJ]

Either start the slot from and angled plane, or (as attached) use an axis (or and edge) to define the extrude direction.