Thick cardboard, I also pick some up in black
timber in all sorts of shapes and sizes
Fabric, these came in a bag full of samples but they also have rolls of fabric.
So far the kids have been making model houses and furniture to fill them.
I have been making fabric flower brooches (sorry, they haven't photographed very well, they look much better IRL)
Here we have hessian bags, leather pieces, linen fabric, jars, buttons, double sided tape and cardboard tubes, small ones in this case but they also have huge ones.
I found everything to make this practical and pretty jewellery board including the frame which a painted and distressed, the foam, the backing board and the fabric. The pins came from my scrapping stash. All up this would have cost me no more that $4 max.