Yay! Finally it's done. I hope the next pillow I make goes a lot quicker than this one. I simply stitched the edges together, without cord or other trim. I wasn't sure how the two patterns would look when it was all put together. The edges match up nicely, though. The points on the front and the back lined up and the colors all went together.
It's like having two pillows in one. It certainly brightens up my sofa!