You're doing it right. You continue working with the yarn that you cast on those 18 with and finish the front.
When it comes time to do the top edge of the pocket, you just start knitting with a new strand for those stitches and weave in the end later.
"Trust the pattern!"
Time flies like an arrow, but fruit flies like a banana.
Hop aboard while we follow the cloud-covered van of knitting harmony, man!! Woooo!! --Hedgehog
IngridKH on Ravelry