For artworks on stretched canvas I use below packaging:

1) Acid free tissue paper or butchers paper
2) Several layers of bubble wrap, securely taped down ensuring the corners of the work are sufficiently padded and protected
3) Cardboard box
4) Fragile tape and stickers are used to make sure the artwork is carefully handled by couriers

For extra-large artworks extra-heavy duty cardboard is used.
For artworks on paper I use foam board to protect artwork from both sides.

On rainy days I add cling wrap/plastic wrap to make sure box gets to collectors nice and dry!

As well majority of the times I use recycled boxes in which canvas came from suppliers so I can reduce my impact on environment from packaging. Thank you for supporting me and sharing my love for sustainability.