I think he discusses it after the section detailing his 3 card routine. I can't be certain, I don't have the book with me now 'cos I'm at work.
The Velvet Turnover is perfect for table work, but for standing up situations, not so good. This is because the angles involved are covered much better if the performer is seated.
Derren's card material is performed mostly with a table. You might want to take note of that when learning effects from his books.