Fold the bias strip in half lengthwise with the right sides on the inside.
Sew a seam just under 1cm along the raw edges to create a tube. You don’t really need to pin, you can use your fingers as pins to hold the layers together as you sew.
Turn the tube the right way around. I’ve used a rouleau turner here but you could pin across one end and push it through with a pencil instead.