Colouring surface

[hedwigismyowl]

Hi
I've started colouring whilst watching tv sat on sofa. I'm finding the colouring books too soft to lean on and so would like a firm surface.

I've been using random items like cardboard boxes or hardback books to no avail.

I also stamp things and then colour for making cards so need something better.

Thanks

A lap tray? https://www.hobbycraft.co.uk/crafts-hobbies/craft-tools/lap-trays/

My immediate thought was one of those lap trays with a beanbag bottom.