help with scrappy quilting - material identification

[SnoozingFox]

I have fallen down a rabbit hole watching upcycling and repurposing reels on facebook.

https://www.facebook.com/p/Artefact-100063505039130/ This account appears to be Indian (?) and the women are super creative with what they do - I am thinking of attempting something similar with the fabric scraps I have. What are they sewing onto as a foundation though? Is it paper? can't be, surely? Or an interfacing sort of thing?

Any ideas?

Looks like medium weight interfacing to me.

Yep, but I've done similar with the very very cheap £3 a blanket fleeces from Ikea and it's worked well. Would work sewing them onto anything with a bit of stability to it really.

Calico? Plain sheet?

Nappy liners.

It does look quite stiff when she's flicking through them which makes me think it could be paper - you just tear it off when it's done. I think it's called foundation paper piecing but whether that's for the scrappy look or more precise designs I don't know.

Looks like interfacing but you can do crazy patchwork on calico or no backing at all. I’m making this without any backing…

Freezer paper is supposed to be very good for the purpose, and I once did a similar quilt to that shown using non-stick baking paper under each block, which I then ripped away before making the quilt sandwich. More recently I made a scrappy cushion cover with slow (hand) embroidery instead of machine quilting, and for that I used a thin white cotton underneath so that I could put whichever section I was embroidering in a tensioned ring.

you have a choice either directly onto a backing fabric or as is my preference onto dissolvable embroidery paper that machine embroiderers use. You can do it onto paper and pull the paper away at the end but I don't like the feel or the faff of doing it

I use old cotton sheets as a foundation, cut into squares.
There's a similar technique called Bojagi or Pojagi
https://dizzyquilter.com/2021/01/11/quilt-lab-bojagi/