Here is the part that is going to save Rapunzel!
I am going to knit one row, then on the next row, I am going to pick up a purl head (a Purl Head is the top of the purl stitch that faces you on the right side of your knitting. I always think of Chicago's homeboy Eddie Vedder when I say or write this because I am a Pearl Jam Head...).
I will knit the picked up loop together with the first stitch on my needle.
This will attach the I-cord to the sweater with NO PESKY SLIP STITCHING!
Because I am attaching the I-cord to a part of the sweater that is worked in Seed Stitch (K1, P1), the Purl Heads are very obvious and just screaming to be picked up and knit!
So I will attach the I-cord every other stitch on the angled bodice. I'm working the piece flat on my lap for ease of view and to help keep the angle *straight*. It's D**n cold here in Chicago, so it's also acting like a cool lap robe fo me :)
So here's my technique for Rapunzel:
Row 1: Knit all stitches then pull yarn snuggly across back of work and slide all stitches to right edge of needle.
Row 2: Pick up a Purl Head from the bottom of the head and K2TOG with the first *real* stitch on your needle.
REPEAT these two rows until I-cord is attached around the area you want it to be.