Pocket help!

Okay I’m trying to knit a pair of wool pants (longies) and I want to add some cargo pockets. Do I just knit them flat then sew them on or is their another way to do it?

Here’s a site that may help:
http://www.studioknits.com/bookpage44.htm
I’ve never tried it but bookmarked the site for that “just in case” in the future!