They look similar to the balls of fabric my Mom prepared for her rug weaving.
She would cut a short strip - twist it to tst for "bulk" - and after she determined an appropriate widtu, she either cut or tore her strips.
Then she sewed them together diagonally - no bulky joins for my Mom
She usually folded the raw edges in as she rolled the long strips into balls - she did not like the ragged look
When she was ready to weave it, she would wind it on a shuttle.
She much preferred weaving with materials she prepared herself!