2 1/2" squares will make a 6 1/2" square 9 patch. The corner blocks for the snowball will be 2 1/2". Draw a line from corner to corner, line the little square up exactly with the 6 1/2" snowball square (all four corners). Stitch one thread width off the line (toward the corner) to allow for the fabric used when you press the triangle toward the corner. Make just one of each and check to see if the seams the line up before cutting more. I cut off the under part of the triangle to reduce bulk, but some don't.
The rose fabric - found it in the church storage closet - probably from the 70s, but I still liked it.