USCIS - General Tips on Assembling Applications for Mailing - Page 6

We can send it in a box?

I don't see why not. As long as the box is properly labeled and addressed and all the documents inside are well organized. I don't see anything on the USCIS site page on General Tips on Assembling for Mailing prohibiting sending document packets in a box. It's just a container. What's important is what you put inside it :P
It's not like the USCIS workers don't know how to open a box.

Who knows, maybe I'm the only crazy one whom sent their packet in a box.

You don't need to purchase a box.

Most people's DACA packet should fit inside the USPS Express Mail Flat Rate Envolopes (12-1/2" x 9-1/2") which runs $18.95 for the service. If you need a little more space try the Padded Flat Rate Envolope (12-1/2" x 9-1/2" ) or the Legal Flat Rate Envolope (15" x 9-1/2"). You don't have to send via Express Mail either if you're not in a hurry. For cheaper alternatives, you can send via Media Mail, First Class, Priority, or Parcel Post. It's up to you. Just make sure you send it to the proper address.

Which address should we use if we are sending it via USPS Legal Flat Rate Envelope (Priority Mail)?

(if you are in IL)

Priority Mail Legal Flat Rate Envelope should go to the

USCIS
P.O. Box 5757
Chicago, IL 60680-5757

As far as I know, the Express mailing address is specifically only for the Express mail services.
Priority Mail is different from Express Mail.

I called the Hotline and I talked to a lady that supposedly knew what she was talking about (the first lady didn't know and so she transfered over to a higher up), and I asked what is preferred, a box or a large envelope. She said a Large envelope is preferred, but she didn't outright say that they'll deny a box.

How are people generally putting in the passport sized photos? Like do you just put in a paper clip?

When I got them at Walgreens they put them in a tiny little envelope, so I just paper clipped that. Anyways, I'm sure you'll be fine if you paper clip the actual photos to the packet.

I saw this on the unitedwedream.org facebook page this morning

Thank you very much for taking the time to call! That sort of eases my mind a bit.

Ideally I'm sure they much prefer small, thin envelopes with exactly the evidence they're looking for with no more, no less.

But the reality is, I don't know how well they'll scrutinize certain evidence as "proofs", and it's best to have multiple sources and exhibits just in case. And the packet just keeps growing and growing

Which tabs at the bottom are you guys using?