You're using 'practical' in the wrong sense, but you knew that. Point being size doesn't matter as long as it's surrounded by conductive material. It can be solid or mesh as long as it is sufficient gauge and completely surrounded. A metal shed would work. So would a shipping container and a bucket with a lid or a chainmail suit.
I mean that, for people like me, without a place to put a shipping container, it is not a practical solution.
Also, a fine point, but one that is important: A metal shed or other container will not be a perfect Faraday cage if a portion of its structure is not in electrical contact all around its boundary. My guess is that most metal sheds would lack a metal floor or would have sliding doors that run on plastic rollers and don't make electrical contact all along their peripheries or would have painted panels that don't make effective conductive contact along their seams to other panels.