It's actually just a "square in a square". Put a small square in the upper corner of your large square, draw a line from corner to corner and stitch on that line (note direction of line). Fold the fabric back and press-should be square with your large square edges. You can trim off the extra. Then repeat with a square in the opposite corner. Add the last 2 small squares in the same way. Just work on opposite corners and press after each square is sewn on. Hope this helps-it's a pretty block.