I'm trying to determine the best/most economical way to ship soaps in a box. I have searched this website for info related to this question, but the threads are fairly old. I have also looked at USPS, but their small boxes are too small and then the next box up in size is a huge leap up that is way too big for the number of soaps I usually ship (10-14 bars). Do y'all use USPS boxes or buy your own?