Spool-knit animals

I stumbled across these spool-knit animals online by chance.
They’re animals made from these knitting cords (Strickmühle).

Has anyone had any experience with these, or tried making them before?
They actually look pretty cute, but how do you hold it all together—sewing or gluing?

I just searched on "Ecosia". The little animals look cute. The penguin and piglet are really sweet. I could imagine that they are sewn, and whenever you finish a round, it is filled and stuffed with batting. 

For me it would be a challenge; I already have trouble with small crocheted animals.

Maybe there is someone who has already tried it and can tell us something about it. I would definitely have yarn scraps and a knitting Nancy in the drawer.

Thanks for now, Petra. Maybe someone else will chime in with some tips.