One of the problems with the cut triangles is that they are now too small for the size of your larger squares. You can do one of 2 things. First off, I see that you cut the corners off your larger squares. So, I think the best and most cost effective way to fix this is this: Do you have more of the fabric that you are using for the corner squares? If you do, recut the squares. You can lay them RST on the bigger squares and then use the cut line as a guide and sew a scant 1/4" to attach the corner squares. Iron them open and trim them up to square your block.
The second way would involve cutting your larger squares down to fit the corner squares (which are now triangles). This is going to result in a much smaller snowball block.
Beautiful fabric!
Edited to add: Oops! Looks like a previous poster gave you the same information as I did!
