To knit interior pockets, you knit the pocket lining as big as you want the pocket but don't cast off. (let's assume you've got 20 stitches - you need to know how many later).
Then knit up to the top of where the pocket will be on the main piece.
Knit along to where you want the pocket placed, put the next [20 in above example] stitches onto a holder and knit the 20 from the pocket lining, then finish the row as normal. Carry on knitting till you've finished.
You can do a few rows of rib on the stitches you put on the holder to finish off the front edge of the pocket, and cast off.
But you'll still have to do some stitching to close up the edges of the pocket lining and the top rows of rib.
Hope that helps