This is interesting, they were using bast fibers from oak trees, or fibers that sit between the bark and wood of the tree. They are soft fibers that can be collected and weaved into cloth.
Wikipedia has an article (1) and pictures of modern bast fiber weaving in Norway.
Wikipedia has an article (1) and pictures of modern bast fiber weaving in Norway.
1- https://en.wikipedia.org/wiki/Bast_fibre