At first I thought, why would I make this if I have a compound miter saw? Then…it dawned on me that jigsaws are cheap ($20), and you can use them to cut light metal, which I guess I could do with a blade swap on the miter…which FYI takes 10 minutes. My 2 cents, I would find a better way to mount the jigsaw so you don’t crack the plastic case.
https://www.instructables.com/id/DIY-Jigsaw-Crosscut-Sled-Perfect-Jigsaw-Cuts-Every/