I used black polar fleece .... it holds everything well.

I've even put fully assembled quilts onto it ... without pins!

I did something similar - foam insulation board, covered in the flannel stuck on with small applique' straight pins. I have mine leaning against a wall. Love the size!

I had limited space at one time and purchased jigsaw holders. The kind you fold or roll up keeping the jigsaw safe when not doing it. It has a felt cover which holds pieces still. If you use the roll I place a piece of paper over the pieces before rolling.

I use flannel on mine works really well.

I used flannel over big pieces of insulation from the home store and covered it with flannel. It works great.

First I started with a flannel-backed tablecloth. That wasn't big enough. Then I went with a flannel sheet. The blocks barely stuck, I ended up having to pin everything to it. Then I went with W&N batting, which has worked the best by far. Everything sticks without pins, even when they're sewn together in rows and are heavy. And it's only the batting - no foam boards.

I use a foam board with QD 80/20 batting stretched over it. Holds everything, is light to move, and is firm when you press a block on it.

My planning wall is actually made of homosote (also called builders board) covered in batting. It is heavier and I can stick tons of pins in it without it doing damage to the board. It is not portable, as it is quite heavy. This is a permanent solution.

I use a 1 inch piece of high density foam insulation (from Home Depot) covered by batting. I use spray glue to hold the batting in place - works great! The high density insulation makes it more pin friendly.