Can't you just set the work at an angle in the vice, one of the little digital angle boxes will set it to 0.1 degree.
If you use a saw for the sides then small flycutter like I showed above will flatten teh bottom & get into the corners.
Does it even have to be cut from one piece, you could fix two strips with a 55deg angled edge to main part, thats how I did this one

J
Edited By JasonB on 23/09/2014 15:14:03