I'm knitting some fingerless mitts, and I can't figure out what I'm supposed to do on one this row: "Slip the first 11 stitches onto waste
yarn, cast on 5 stitches, join and knit around."
Okay, so I'm supposed to slip 11 stitches onto a separate piece of yarn, but I'm having trouble with the casting on part. I cast on 5 stitches in the middle of the work? How and why? Can someone explain this to me, please?