I cover the artwork with Acid free paper to avoid contact with other materials.
Inside a layer of cardboard to ensure the artwork is safe on both sides. Then place it inside a bag to waterproof it.
The Outside Foam boards works as - I love to call them - "insurance walls".
is to place corners and bubble wrapped the art.
Corrugated Mirror cardboard boxes. Designed to create a "custom fit". Panels has messages to protect the valuable piece of artwork.