I laid it out so I would match the plaid as close as possible, the horizontal is a closer match than the vertical will be.
I also cut it out, while I still had it laid out on the floor. I would rather not cut on the floor but sometimes it is easier.
Then I sewed the front sleeve to the back sleeve, and rolled and sewed around the split in the sleeve.
I’m still not so sure I like the 2 piece sleeves but it was easier to finish off than a slit cut in and a small bias but binding.