This is a basic little square pattern that can be extended by going to my
http://www.ravelry.com/patterns/library/rock-solid-granny...

Please note, the stitch counts do not match between the two styles. The Rock Solid Circle in a Square has 8 stitches between the corner stitches in the outer row – which is roughly equivalent to row 3 in the Rock Solid Granny Square which has 7 stitches between the corner stitches.
So row 4 in the Rock Solid Circle in a Square will have 11 stitches in-between, Row 5 will have 14 stitches in-between and Row 6 will have 17 stitches.
Regardless of the slight difference, the patterns are worked in the same style; you will just add one more stitch in the middle of the row between the corner sections. You still flip your work over in Row 5 and any alternate row after that.