First and foremost, ensure your resined artwork has fully cured for at least 72 hours before packing or transporting your art. Although it may seem cured after 24 hours, it has not had a chance to cure all the way through and could be prone to indenting.
The best material to use against the surface of your ArtResin epoxy resin piece is glassine paper. Glassine paper is smooth, glossy, acid-free and will protect the resined surface without scratching or sticking. Once your piece is protected with glassine, you can pad it with poly foam to provide cushioning. You can further pad your piece with fabric and cardboard or foam core for extra protection.
If you choose to use bubble wrap, DO NOT use it directly on your artwork as a first layer - use it as exterior padding only. Always make sure the flat side is facing in and the bubble side is facing out, otherwise there is a chance the bubbles may leave an impression.