Here is the link to the pattern I used.
However, it is not a square pattern. It is for a scarf or cowl and I just stopped when I got to 8 inches :) Your piece will look very 'wonky' when you start, but it will even up as you work along. At some point it will be square ... unfortunately, I can't say which row that is because I didn't keep my notes :(
Also, it will need blocking to 'look' square, but I'm sure if it's not blocked it won't matter once it's stitched in with other squares in S.A. ... xo