You'll need four different colors from your "blocks" fabric for this block, so select four and designate them #1, #2, #3, and #4.
You'll need:
Eight 5" squares of background fabric
Two 5" squares of fabric #1 (Zigzag)
Two 5" squares of fabric #2 (Blue)
Two 5" squares of fabric #3 (Grey)
Two 5" squares of fabric #1 (Zigzag)
Two 5" squares of fabric #2 (Blue)
Two 5" squares of fabric #3 (Grey)
Two 5" squares of fabric #4 (Green)
Using the directions from this blog post, use the above fabrics to make 16 half square triangles. Arrange them as seen in this picture.

Sew them together into four rows