I slightly adapted my Leg Warmers Pattern to include lacing up the back of the calf.
My etsy shop has the original pattern:
Every other row I added 2 chain 1 spaces that were 5 stitches apart (child size). I did a dc in the chain spaces in the opposite rows.
I then took a long piece of yarn and laced through the holes to get an idea of how long I would need my pink lacing to be. I used this yarn to gauge how many chains I should make so that it would be long enough to complete the lacing. After chaining, I slip stitched in the 2nd chain from the hook all the way down to last stitch. You could also use ribbon or braided yarn for the lacing. This is an easy way to adapt your leg warmers so they can match different outfits!