This block could theoretically be rotary cut and pieced, but I just find foundation piecing so much more accurate. If you made this by rotary cutting and want to share your method, let me know and I'll link to your blog.
Print or trace the diagram onto your foundation paper.
You have to mirror the diagram.
My numbering and sections were as follows:
Foundation piece each section. Remember to leave a ¼" seam allowance all the way around. Accuracy is important here because you want to be able to piece them together.
Make the side triangles first.
Attach them to the center strip.
Here's what I do to help with accuracy in doing this.
Mark the center of the strip. It should be 7" from end to end, which means you will make a mark at 3.5".
Mark the center of the middle section on your triangle. It should be ½" wide.
Wrong sides together, line up the center strip and triangle, matching those center markings.
Stitch about ½" of the seam in the center. This way the centers will be lined up. I've found that, if I start sewing the seam at the end, the fabric shifts and by the time I get to the middle, the centers aren't lined up any more.
Now, starting at each end and lining up the fabric edges, sew towards the center, overlapping the ½" section you've already sewn by a little.
Repeat for the other triangle.