Concrete pad for shed

I'm laying a concrete pad for a garden shed. Some of the sides of the pad are going to but up to existing brick/stone walls. I gather I cannot simply use the walls as formers and pour concrete straight up to them.
I guess I need to attach wooden boards to the walls, and pour the concrete up to them? Should the boards be removed when the concrete has set?
Thanks for any advice

Ideally yes, or else the wood forms will rot over the years and his will cause a void where they have been placed, I would leave a small gap to get the boards out and then fill that gap with concrete to the correct level while the concrete is still green.

You could just use a couple of layers of heavy polythene at a stretch. Or a 25mm sheet of polystyrene, which can stay put.