I wanted more white in the room and the space behind my chair was just the biggest bit of wall space that could take a design wall.
I used some leftover packaging (extra thick corrugated cardboard) and duct-taped the pieces together to make one big rectangular-shaped board.
Once you have a board of the size you want you need to cover it with some sort of material that will help your quilt blocks stick to it without pins.
Note: This bit is totally optional – you can absolutely make a design wall free-standing if you like.