You knit into the stitch as normal, but don't slide it off. Bring the yarn forward between the needles and purl into the stitch again, but don't slide it off. Keep knitting and purling and knitting into the same stitch and only slide it off when you've done all the stitches in it. Then slide it off.
"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