Taming Curled Cast-On Edge

I did another swatch ...

As you can see, the first one on the right is curled up at the cast on edge when not pinned down.  My second swatch (on the left) is not! 

I used a cast on method with one-by-one cable pattern described here.  The rest of the instruction is written as if to knit in round while the swatch was knit flat.

• Knit the first round in solid dark color in the rib pattern. 
• Knit the next Fair Isle round in the rib pattern using Elizabeth’s purl-when-you-can method (the stitches in lighter color in stockinet).
• Knit the next two Fair Isle rounds in the rib pattern.
• On the next round, knit stitches in lighter color in stockinet and those in darker color in the rib pattern. 
• On the next round onward, knit all the stitches in stockinet.

The second one is better than the first in terms of curling, but it is a bit uneven and actually look a bit thicker at the bottom.  It is because of the ribbing on Fair Isle rows.  When I used the rib pattern over a few rounds only, the edge was still curling.  Thus, I continued in the rib pattern for four rounds. 

I am ready to cast on for real!