I’ve been wanting to do a few little things like this for myself, to see, to figure out, what really works best? And then Sweater Club came along at my LYS and I decided this would be a fun little project.

I CO 44 sts, worked a few rows in St. st, and then worked three sections for a pocket.

A: The first pocket (bottom) is a patch pocket. Work sweater, bag, etc. first. Then, knit pocket patch (teal portion) second, bind off, and sew to project in preferred spot.
This pocket would be most successful if the top (garter band) of the pocket were knit on smaller needles, which would help with the sagging. This pocket sticks out the most but is definitely the easiest!

B: The middle is a set-in pocket. First, knit a flap (teal portion - see back, 2nd picture), but do not bind off; leave on stitch holder or spare needle. Then, work project to preferred location of top of pocket. BO sts where pocket will fit in. Next row, work to BO sts, work pocket flap in from st holder / spare needle, then continue on with project. When finishing, whip stitch pocket flap to inside of project.
In my opinion, this method had a tidier look around the pocket, but the top was more sagged and therefore less desirable. It also takes some planning ahead, a spare needle, and will have no flexibility should the knitter decide it should be lower / higher, etc.

C: The final (top) pocket is an afterthought pocket. Work project as written, without pockets. After the project is done, decide where the top of the pocket should be, as well as left-to-right placement. SNIP ONE STITCH where the top center of the pocket will be. Unravel this row of stitches to the left and the right, putting live stitches from above and below on dpns or circular needles (above on one needle, below on a different needle.) You should unravel to the right for half the sts, and to the left for half the sts - example, for a 22 st pocket, unravel 11 sts left and 11 sts right. You now have a tail at each end of the live sts that can woven in later. For pocket flap, working on wrong side, join new yarn (teal section, see back - 2nd picture) and work from live sts at top of hole that was created by unraveling sts. Work back and forth to desired length for pocket. BO. For front edge, join new yarn and work from live sts at bottom of hole and either BO, or work back and forth to provide nice edge, then BO. Sew pocket lining flap down on WS of work; sew edges of top edge down on RS. Weave in ends, etc. including the two that were unraveled.
This method - cutting perfectly fine knitting - is not for the faint of heart. It also cannot be moved once you snip! However, it is a great option when you knit the perfect sweater, and then decide it would have been even more perfect if you had added pockets!! To keep top of pocket from sagging, work top of pocket (garter section) on smaller needles to tighten up gauge. I forgot to switch to smaller needles, actually, but definitely will do next time!

And there you have it!