Even with measuring I cut off a couple of elements to make my panel fit. Here are some steps I took to attach my panel....
I made a pattern that fit perfectly in the space I wanted to fill. I used pattern tracing paper so I could see through it. When I had the perfect fit, I laid it over my improv panel and two layers of cotton flannel. Then I cut all three layers into the perfect shape.
I bound the edges of my layers with a single layer of 2 inch binding. I used bias cut strips to accommodate the curves on the sides of my pieces. I sewed the binding onto the front and neatly folded and pressed it around to the back. I didn't worry about the raw edge on the back since it would be completely encased.
I pinned my piece onto the jacket and machine stitched all the way around at the outer edge of the binding.
I wanted to secure my piece to the jacket back so it didn't pull away. Using size 8 perle cotton thread I stitched xs, running stitches and chain stitches embellishing the improv piece. My stitches went all the way through the layers attaching them to the jacket. And yes, you can see the back of my stitches inside the jacket.
I really love the end result! I did add a few embroidery stitches to the front of the jacket just for fun but the real party is all in the back! Will you be making one too?