I worked this using modifications by Scraplyn (on Ravelry), and I quote:
I changed all TR to DC, DC to HDC, and HDC to SC. I left the SC alone. In round 5 I changed the CH6 to CH4.
I did find that the square would not lay flat for me, but the first one didn't either. Same pattern of pucker, just on a smaller scale. Perhaps it'll straighten out when it's attached to other squares. We'll see.
Pattern link on Ravelry.
Bernat Super Value: 53044 True Grey
Bernat Super Value: 07711 Navy
Hook used: I