Originally Posted by BlueChicken
Sewing the square is an easier way to do it, because you don't have a biased edge that can stretch. If you don't have a 1/4 inch foot for your machine, simply draw your line from corner to corner, then draw another line on each side, exactly 1/4 inch from the first. Sew down those lines, and voila! :-)
This is exactly what I was going to say. I have a 1/4" foot, and if you can get it for your machine, it's a very good investment.
If you move your needle to the right, can you get the distance between the needle and the right side of the presser foot (or one of the lines on the machine) to be 1/4"?