can i send usps priority mail flat rate envelope from personal mailbox

The eBay shipping options do match the USPS Priority Mail items.

Thanks so much for any assistance, shipping charts etc you can lend

Can you use your own packaging for priority? Can you use your own for flate rate priority? I know you cannot use flat rate packaging for anything other than flat rate. I also thought you could use your own packaging for priority. I do not have a store or anything, is that why I cannot see all the shipping options? (Like flate rate shoe box, for example). The ebay USPS shipping options don't match all the different boxes and envelopes available for USPS priority. I paid over $12.50 to mail this package-100% loosing money on an item that sold for 12.50 before fees and shipping I was only going to make $4 or so anyway. Or that they had billed up to that amount. Plain old priority mail was only $10 something and I wish I had used that instead. Then when my boyfriend dropped it off at USPS, they charged him another $6.10ish. I know there's a billion people explaining prority mail but I'm still just not getting it! I paid about 6.50 for a box in a padded envelope in a poly mailer-did not use any free priority boxes. I tried to ship something by 'padded flate rate envelope' setting on ebay, because I misunderstood a youtuber saying to use the 'package/thick envelope' setting to ship priority by weight.

Can i send usps priority mail flat rate envelope from personal mailbox