Knit the cuff of your sock in stocking stitch until your yarn changes colour. This is what signifies that it is time to use waste yarn to work your heel stitches.

Knit to the end of the needle you are currently knitting on. Now, with the yarn still attached to your work, wind the heel colour into a mini ball. Cut your yarn, the mini ball will remain attached to your sock until you come back to complete the heel.

Now take the yellow waste yarn you wound off before you cast on your sock. Use it to knit the next 2 needles, making sure to leave a tail at either end.

Re-attach your main yarn and knit across your next 2 needles. Place a yarn marker to mark the beginning of your round.