When you start to knit the ribbing you can check as you go by simply pulling on the front and back pieces of the pouch and make sure they separate. If so, then keep going until you've finished the ribbing.
Then, when you slip your stitches onto the holding needles at the end the pocket will magically open. Then you can just bind off each individual (now separated) stitch.
- 0 - 0 - 0 - 0 - 0 - 0 - 0 (unseparated stitches, all on one needle)
- - - - - - - - - Back stitches separated out
0 0 0 0 0 0 0 0 0 Front stitches separated out
Hope this helps!
In progress - designing, knitting and writing a knitting book, "Design Your Own Gourmet
Kitchen Cloths and Accessories".