Copious Free Time Meaning

(idiomatic, sarcastic) A hypothetical time set aside for performing time-consuming tasks, however insinuating that the speaker really has no free time.

Example:   I'll do that in my copious free time.
1959, Tom Lehrer, introduction to It makes a fellow proud to be a soldier:
  I recall this sergeant's informing me and my "room-mates" of this rather deplorable fact the army didn't have any official, excuse me, didn't have no official song and suggested that we work on this in our copious free time.