The sleeves will be worn with the last 20 cm folded back.
I cut out the sleeves from linen. The last 23 cm will have wool inside and outside too, so that the lining does not show. When I iron the seam between wool and linen, the seam allowance always aims to the lining piece.
I sewed the lining and upper sleeves together at the lower edge. I could have had cut out the wool panels from one piece, but before the last trial I had not known how insanely long the sleeves would be :-D
I cut out the seam allowances at the sleeve to one centimeter. I aligned and pinned the lining so that it lays flat and cut it half a centimeter longer.
Sleeves are now prepared to be inserted.