I do as Tartan does. I make my square in a square blocks this way, too,just a modified snowball. when you sew along the marked diagonal line, make sure to sew next to the line, not on the line.
I don't have waste with this message because I sew an additional diagonal line about 1/2 inch away from the true needed line. It gives me a bonus half square triangle that i can use either in the quilt border, on the quilt back, or in a random scrap block.