PicoCTF 2014 PNG Or Not?

I was given a png image and told that there was some data hidden within.  If you do a Google searches on PNG files, you will note that you can hide files in it.  I opened up the image with a hex editor.  Near the bottom of the file, I found 7z, then the words flag.txt.  I know, from reading articles, that I can carve files using headers and footers.  I knew that the header for a 7z file is 37 7A BC AF 27.  I just selected the bytes from that header to the end of the file, copied it onto another sheet in the hex editing program and saved it as a 7z file.  I opened up the flag.txt file using the archive manager, and I got the flag.  EKSi7MktjOpvwesurw0v

Update:  Easier Way:  Command line:

7z x 2pngornot2png.png

Then

cat flag.txt