depends on the quantity and size. ive shipped small snails using the plastic sauce containers with moist paper towel and floaters, lid taped then placed within a plastic ziplock, then wrapped in a paper towel, then placed inside an insulated envelope for shipping.
larger orders, ive done the same but in a quart container with multiple wet paper towels, plants and tape pint containers then filled with paper insulation in a USPS priority square mail box which you have to order as they arent available at the post office.
sounds like a lot of work but i havent had any losses reported since and these guys are stronger than shrimp.