I'm sure your approach would work. The piece would look like the plates are floating. If that is the look you want (instead of sashing between) then go for it.
If I were doing it that way, I would work from the center out. When you position each plate, add some tear-away stabilizer on the back. That way your pieces won't distort the backing fabric. I tend to stick my applique down with tiny dots of Roxanne's glue baste. That way nothing will shift when I actually sew the applique down.
I would make a plan for layout ahead of the game but I would only attach one plate at a time so the pieces won't get in the way. It will still be a lot of fabric to pull under the throat. As a beginner you may not be doing yourself any favors.