After you hand in the application and get the acceptance decision, you can produce samples on a trial basis before the field verification, but you are not allowed to sell them.
But in practice, you can produce a few days in advance, and as long as the local bureau doesn't care about you and gets the records right, it doesn't matter.
But you produce more, if you can't pass the field verification then you have to declare again after 3 months. Time will be long.