My understanding of the OPs question (maybe I got it wrong) is that the OP wants to book a flight that is 3 days out (assuming availability). In order to not pay the close in fee, he will make a reservation for 22 days out, and then change it within 30 mins of booking to his desired date hoping that it’s within 24 hours and a lenient agent or wacky website will allow it to happen without a change fee. Not sure if it’s gonna work now but it did work a few years ago when close in fees were introduced.