Take a hot glue gun or glue dots & layer the small solid feathers onto the barrette cover as desired so the barrette cover is completely covered with the feathers, you can overlay the feathers a bit & then trim them down once they are glued for a clean finish on the edges as well.
Next take the large peacock plume & center it in the middle of the cover & hot glue the back of the bottom plume then secure into place. (You can also run some hot glue down the spine of the plume to secure it better if desired)
Once your feathers are arranged as desired, you can put the finishing touches onto the clip by adding a few of the rhinestones to the base or on the peacock plume with hot glue. Next flip over the barrette cover & hot glue the alligator clip to the back so the clip will be facing the direction you would like it to hold the hair in place once it’s finished.