After interfacing where needed, I sewed up the back seam, and "uh oh." This just didn't look good. I had cut the back pieces double, and the pattern repeat was too off to match, but too close to look random. I debated leaving it alone, but decided that the only real choice was to rip and re-cut one of the back pieces.
But how? Match the print across the seam? I really thought about doing that, but a couple of issues came up. The fabric wiggles. A lot. Like if you breathe on it, it moves. So matching would be pretty difficult.
The second factor involved the print. Large and small circles. What if I did get that back seam perfectly matched and it ended up with a perfect bullseye on my butt? That would be terrible after all that work.
So I decided to make the seam look random. It actually isn't.
Here's what I did. I laid out one of the previously cut pieces on the fabric. Both the yardage and the cut piece are right side up, just as it would be when sewn. Note that I didn't press out the seam allowance or the slit. Once I decided on a nice appearance, I made sure the fabric was on grain. Then I pinned just beyond the folded-under edge of the cut piece.
Here's another view of the pinned seamline after removing the cut piece. The seamline has also been marked on the pattern.
This photo shows the pattern laid over the pins, with the pins and the marked seam line aligned.
Here's the completed seam after being pressed flat. A lot better, isn't it?