I tend to agree, it does look like HST's with small triangles added to two corners opposite the seam. simple but you just have to be sure to get all your triangles sewn the same way/size. so they will all meet up well to form the "diamond".
and i've done 10 minute blks with different inserted square sizes. they don't all have to be the same size. you get different looks doing that.
have fun!!