The best way may depend a lot on what your machine is, what tooling you have available, and even how many of these parts you need to make.
If the part is a low volume part, positioning the part at the correct angle to the head in a fixture and mill the angle with an end mill on a manual machine. Or if you have a multi axis machine (4th or 5th axis) that can mill at the required angle. Another option would be to use a profile mill with the proper angle built into the tool. And of course using a ball end mill to approximate the profile with many passes is always an option.
