If you sew it right sides together to a light weight fusiable interfacing. Then cut the center of the interfacing away. Turn it right side out, smooth the edges, then press it to the background fabric. You can then use a blind hem stitch or just straight stich around it.
That being said, I have never made a dresden plate. If you sew the petals together first you could use one piece of light weight interfacing on the back of the plate instead of doing each petal seperately.
Linda L