I followed this scarf pattern, starting with 36 stitches to get a 9" square. It was so fun to use that I have made a total of 3 squares in this pattern thus far.
Outside In Squares
The concept for these squares is really intriguing, you knit the square in the round where the CO edge is the outer edge of the entire square. I needed to reduce the number of stitches since I only had size 9 round needles of the right length (the pattern calls for seven). My pink square is about 0.5" too large in all dimensions, but I'll still incorporate it into the blanket. I reduced the number of CO stitches by 16 in the black square, and it is the correct size.
If the size were drastically wrong, you can measure the progress of the square really early on in the project.
The finished squares.
I started with this scarf pattern, casting on 34 stitches.