Wrapping a fragile item: Best to use bubble wrap. Wrap significant amount portions of the fragile item (see above 5 centimeters = 2 inches), giving extra wrap in more damage prone areas, then wrap the entire item in bubble wrap with packing tape to keep wrapped during shipping.
Here are some good videos about packing flat artwork. Instead of the crate or plastic systems employed, we recommend www.thekubox.com as this parcel crate system is used by both galleries, artists and collectors. There are many DiY solutions but we believe that artists probably want to spend time on their art rather than time on building shipping systems.