[mothered]

I am not familiar with the empty box method what is that?

As the name suggests, you send the box empty-  without the Item.

Instead, you add dry Ice that matches the weight of the Item, make a tear on the box consistent with the Item's size, and seal It with different colored tape. By the time the package will reach It's destination, the dry Ice would have sublimated (turned to gas), hence empty box on receipt.

So they dont check inside the box once they receive it?

@Auftot has explained It very well, so I won't elaborate further.

Just for your knowledge on how dry Ice works and why It's commonly used when boxing, as opposed to Ice that "melts" (hence leaves traces of liquid), dry Ice "sublimates" (turns to gas). Therefore, upon opening the package, there are no signs of It's preexistence.