I finally finished the first cardigan I started here. I took the long folded fabric from the mentioned post They are 3" wide and as long as the cardigan front) and folded the ends of the fabric inside, then sewed the long sides closed with the openings of the cardigan sandwiched inside.
Then I cut 2 rectangles of fabric twice as long as the sleeve openings are around and 3" wide. I sewed the short ends together to make tubes, then fold the tube in half with wrong sides together and zig zagged the raw edges.
After that, I basted beside the zig zag and gathered to match the sleeve openings.
With my sleeves turned inside out and folded to the right length, I pinned the ruffles on the current outside of the sleeve and zig zagged in place to allow some give. Then I trimmed off the extra material that was turned up.
The circles are cut from my material and scrap from the sweater that I finished with frey check, and attached with a few crossing rows of zig zags.