How to ship items to eBay Authentication facility

[montybendernoodlebeeferolive]

I'm going to be selling off some of my trading cards in the near future, some of which are valuable enough to qualify for the eBay authentication service. The thing I can't find information about is the best way to prepare the card for shipment to their facility. Am I supposed to use a penny sleeve inside a top-loader inside a rigid or padded envelope like I would as if I were shipping the item directly to the buyer, or is there like a special sleeve/cardholder/envelope that I'm supposed to buy from eBay?

[Anonymous]

https://pages.ebay.com/authenticity-guarantee/

[montybendernoodlebeeferolive]

I've seen that page. Unless I'm missing something there's nothing on it that gives information about the best way to package the items for shipment to their facility