I added this photo to accompany the Corner in Shell Block Square pattern, showing a zoomed-in look at the stitches used on the openwork corner of the square. This can be helpful to refer to, while crocheting the pattern for the first time.
If you're looking for the free pattern for the square, see Corner in Shell Block Square Pattern
Click the link named Next under the photo above (and again under the photo on the next page) to see some ways in which the squares might be arranged, when joining.