Being the daughter of a lifelong USPS employee, I've learned a thing or two about mailing letters and packages. For example, did you know that there is such a thing as a book rate (formally known as media mail)? Yep! Of course, some restrictions apply but it's often a rate that many people don't know about.
So let's talk about mailing out your blocks and how to get the cheapest rate possible. I've posted about this method before, but I want to revisit it in more detail. Here are my 2 not-so-secret weapons: Glad Press'n Seal and 6"x9" manilla envelopes.
The key to cheaper postage is getting your package as flat as possible. The envelope shouldn't be padded. What's important about this envelope is the size. A 6"x9" envelope is considered a standard letter size, according to the US Postal Service (see this handy chart).
Now in order for it to ship at the letter rate, it cannot be thicker than 1/4" and it should not be completely rigid. It needs to be a bit flexible so that it can go through the automated sorting machine. If you add in a rigid piece of cardboard it might have to be sorted by hand and that increases the postage. The best product I've found to protect my block during shipping is Press'n Seal. Not only does it protect your block, it aids in getting it as flat as possible. Unfortunately, I don't think that this product readily available outside the US.
So here are the steps I take:
First, I rip off a fairly large piece of it and lay it sticky side up. I include a small note that has the name and address of the recipient, face down.
Next, I fold up my block to a size that will fit in the envelope. I find that you can get it flatter by folding it with the seams on the outside.
I carefully fold the block up in the Press'n Seal, pushing out as much air as possible. I then use tape to secure it.
And here is how thin I was able to get it:
I don't live near a post office, so I always mail my domestic blocks from home. How do I know how many stamps to put on it? I use my kitchen scale to determine the weight of the envelope and go to this USPS site to calculate the postage. Typically, it will require 2 stamps to send a block.
International blocks require a trip to the post office, but I still package the envelopes the exact same way and if you keep it to the letter size, you shouldn't be paying more than $6 to send it overseas.
And there you have it! I hope this helps to reduce your shipping costs. You will find all of this helpful information under the Resources & Tips tab at the top of the page.