Picture of Make $4.75 USPS Flat Rate shipping box
This is my first instructable. I invite feedback, coaching, and correction.

My wife finally started selling stuff on the internet. One of the big things that distinguishes sellers is shipping costs. If what you are selling (in our case used boutique baby clothes) is heavier that 13oz. you have a lot of options* of how to ship. The same package could cost you $8.60, $10.95, or $4.75 depending how smart you pack it. I was able to package 2 shipments by hand in about 40 minutes. Once I made the jig I could do it in 3 minutes flat.

* Technically you have one les option, since the cut-off for the cheaper first class mail is 13oz.  If you can ship first class, you should. It's the best value. So, for packages 13ox and under, I think there is really only 1 choice.
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Step 1: The supplies

Picture of The supplies
Here is what you need.

1. A 12 1/2in x 9 1/2in Flat Rate shipping envelope, price $0.00
2. A strip of plywood* ripped down to a width equal to the shortest dimension of your box, price $2.00 or free (scrap)
3. 8 wood screws 1 1/4in length or longer, price $1.79 or free (scrap)

Table Saw for ripping the plywood (not needed if using a 2x4)
Miter Saw for cutting the sides to length
Philips P2 bit (or T20 if using DeckMate, the only wood screws I use)
Counter sink bit (recess the screw heads, it's prettier)
Forstner bit , Wood Spade , or Auger

* You can opt for a simple 2x4 if you don't have a means of ripping the plywood, but it won't be very useful for stuffing.
foobah12319 days ago

This is prohibited per the Postal Domestic Mail Manual (Eg, postal regulations) If you use flat rate priority packaging, you are not allowed to modify the package shape. It must remain the same shape and size as when you got it - doing this is a great way to have your package get damaged on the sorting machines at the post office and/or have it RETURNED for standard postage (or delivered postage-due)

If you want to make custom-shaped boxes, you can use the NON flat rate packaging materials, and then pay proper postage based on weight/etc.

USPS shipping is far cheaper than UPS or Fedex, why do you feel the need to cheat them out of a couple bucks?

JohnL252 months ago

I use a similar method, often. The envelope will hold more than twice as much as the small box, for the same price. Since it is priority - if the items you're shipping are heavy and/or small - the priority tape is at your disposal; use it liberally. This will keep prying eyes and hands out of the envelope and avoid it "accidentally" breaking open. I mummify my shipping packages at USPS, since I've had bad experiences with them "losing" much of the contents in a USPS facility. Use the electronic kiosk to avoid hassle from nosy USPS employees and speed the process of shipping. I use my phone to shoot a picture of the label before shipping for easy tracking and to send to the recipient.

Super Smart!!!!!!
Winged Fist2 years ago
Great Instructable! Well photographed, tagged and documented!
diylover2 years ago
I love the ingenuity and will give this a try.
According to's flat rate priority mail page:
"Shipping shouldn’t take a lot of time and guesswork. With Priority Mail Flat Rate Boxes and Envelopes, if it fits, it ships® anywhere in the U.S.* for a low Flat Rate. And no need for those zone maps."

lzs3 years ago
If you have any problems with USPS, please feel free to contact us at and post on our wall. We will answer back within 24 hours.


You may submit complaints to grievance through the USPS site. It WORKS! Your local USPS will NOT like this. =D Make sure you leave your actual information when filing a complaint so when your local post office calls you to discuss any matters, you can actually go in and let them see your face. Next time, they will know better than to mess with you!
lzs3 years ago
Right? That's what I thought. Flat rate does mean "flat" shipping rate!!!! This lady from my post office said flat rate means the envelope has to be flat.


My local PO wont accept this, They make you put it into a box. But they arent very nice ever. My buddy calls her the U.S.P.S. Under Sexed Postal Slu!
RichardBronosky (author)  Terry Schmidt3 years ago
If you get something non-hazardous weighing less than 70 lbs (Keep in mind that a solid block of lead would only be 77 lbs) to fit into an intact USPS Flat Rate shipping container and seal it with an approved means, they will ship it. Your local PO is a stickler for policy. They are very unforgiving about it and that's why they seem like such jerks. (Mine is the same way.) Their policy states that my first sentence in this comment is true. They will follow their policy to the letter. If you doubt it, try it. If you have a problem, take down names.
RichardBronosky (author)  redesignsbyd3 years ago
Thanks! I've been receiving mostly negative feedback based on people's bad experiences with their post offices. I suspect those experiences are unrelated to flat rate shipping packages also.

The fact of the matter is this:
This method works for stuffing the maximum content into the cheapest container.
If your contents fit and weight less than 70lbs, they will ship it in these flat rate packages.

I'm glad someone appreciates the idea.
caitlinsdad3 years ago
I don't know about your post office, but here in NYC, you will be subject to the 20-question barrage "Is there anything hazardous, perishible, liquid, flammable....Insurance, confirmation....Would you like a book a stamps?" to include getting a speech on those are flat, meaning flat document, flat-rate mailers, you must repackage that to mail at the regular rate because you can't use an official flat rate mailing box to ship anything other than flat flat-rate. Now get back in the line after you repackage that to be subject to the same line of questioning again. I guess don't try to send anything fragile as it will get it hung up in the high-speed processing machines and your package will get there when it gets there.
"Flat rate" means that you only pay one price no matter what the package weighs.
true, but here you get hassled for trying to ship something like an overstuffed burrito, I'd rather not see them go postal.
RichardBronosky (author)  caitlinsdad3 years ago
I buy postage online. It's built right into PayPal, so you don't even have to copy the shipping address. I can leave it in my mailbox with the flag up or drop it in the box at the PO downtown when I go to work and that shaves a day off the ETA. Honestly I don't care how long it takes. I'm not the recipient. It's cheap and it's easy. No need for negativity. It's really a pretty pleasant experience.