when i applique my plates to the background block i use lots of pins- pin the center circle first- then each plate along a long edge- then last but far from least the points.
i have used fusable webbing a couple times on smaller projects- i cut thin (about 1/4" maybe just a bit larger) strips of the fusable and place them along areas that i (think) will hold it well- i do not put fusable anywhere where i will be stitching- it is a bear to hand stitch through!
elmers school glue works fine too- and probably lots easier than the spray fusable....just put dots here & there- place it where you want it- smooth and flatten- when it's perfect- press it- it will hold= and the glue washes away in the washer when the quilt is done.