This technique works well for items such as sock cuffs as it provides a stretchy cast on edge.

 

With waste yarn cast on half the required number of stitches. While working first round divide stitches evenly across needles

Using project yarn: Round 1: [k1, yarn over] repeat these two stitches around. Round 2: [yarn to back, slip 1 purl-wise, p1] repeat around. Round 3: [k1, slip 1 stitch purl-wise] repeat these two stitches around. Round 4: [yarn to back, slip 1 purl-wise, p1] repeat around.

Remove waste yarn