I think I'd use a Japanese saw. I'd make a small jig like the drawing in a trapezoid shape with the angle you want for each cut, with a small block on the back to hold it in place while making the cut. I'd make the front out of at least half inch hardwood scrap so it will resist being cut in the process.
Hold the dozuki style saw (with the rigid back) as you would a chef's knife, a finger on the side to keep it from shifting on you, then place the saw against the edge of the jig and probably less than 4 pulls and it will cut through, making an extremely smooth edge.
By the time you set up a saw or router to do this cut, you could be finished with the Japanese saw. If you don't yet have a Dozuki saw, you have no idea what you're missing. Once you use it you will reach for it often, cutting is like slicing butter. Here are pictures of the two types of Japanese saws. The first has no backer, the second shows three types with backers. I like the longer saw best Amazon. About $35 as I recall. You can't have these sharpened, so when it gets too dull to use (that will take a long time judging from mine), you replace the blade part with a new one by clipping it into the backer. The backer keeps the blade ridgid and that's the one to get.
My 2 bits.
The more I do, the less I accomplish.
Last edited by DesertRatTom; 01-29-2019 at 12:48 AM.