This flat slip-stitch granny square join is the joining method I used on the Sunburst Granny Square Blanket (see picture below). It gives a flat yet clearly defined vertical and horizontal lines that frame up the squares.
[Update March 31, 2015: If you are interested in the solid granny square crochet pattern, please click here]
The method is similar to slip stitch join I did on the African Flower Purse, but instead of joining at the back of the squares, this flat slip-stitch method is working from the front of the squares.
There are plenty of joining methods for granny square, choose the best to suit your project. Perhaps I should make a round up to show you some of those popular and commonly use joining methods.
I hope this will come soon [Update : Click here to choose from the 12 ways to join your granny square]. Stay tuned! While waiting for that, please click page 2 for the detail tutorial of this flap slip-stitch method.