After pinning in place, making sure each piece overlapped evenly with its neighbors, I basted all the pieces down.
I used needle-turn appliqué and 50 or 80 weight, whichever I had on hand, of Aurifil thread to stitch the pieces down. This was a bit fiddly because of the overlapping pieces. Here it is about half finished.
After appliquéing, I removed the basting stitches. I like how the landscape looks, simply framed, but now I wonder if it would be improved with quilting. There is a slight wave to the fabrics that is bugging me a little bit, even with a few layers of batting added behind it. If I quilted it, I could mount it on top of the mat, rather than behind it. What do you think?