Press seam open, pin down next strip, and QAYG

Again... we sewed two strip sets (right sides together) to the backing. We folded open the strip sets, pressed open the seam, smoothed down the newly exposed strip set, and then lined up another strip set on top of the strip set we just pressed open, again right sides together.
This post might be out of order, but it might not be, LOL. It's the same thing that we're doing with every seam at this stage...

pressing strip sets

And yes, I pressed them closed and then open...