The Final Box is a exploit of limitations of language that would be greater than The Box in terms of cardinality. The Final Box exists so long as The Second Box exists. However, The Box by definition contains everything. So by proposing a Second Box, the Second Box would become the de-facto The Box. But, by exploiting language, we can give it a name called the Second Box, with it still having the same attributes as The Box. No logical system is broken here, as we are merely giving it a name, but not changing its property. We can repeat this cycle until one decides to add the adjective "Final" before The Box. Now, the Final Box is produced.
This Final Box is the last box to contain itself in The Box. The Box cannot contain it. IT CONTAINS THE BOX. Box contains the box. BOx Box. Boxbox. Boxboxoxovbooxoox lol