I think that the spans would be made and served off the ship ( maybe on some sort of a jig ) then placed and lashed in position on the ship,
I completed this sling on my model but I am not sure it is the way it was actually done. At least it doesn’t look like on attached pictures.I bet you already figured out how to do this. I think I saw your newer post of your success.
So, I did see your finished sling and I think it looks perfect. I also saw your post on your rope serving machine problem and knew you would solve it also. Sometimes working out problems gets a little dinghy!I completed this sling on my model but I am not sure it is the way it was actually done. At least it doesn’t look like on attached pictures.
the swelling of the splice was just not shown in the picture.