How do you attach a hanger to a Styrofoam plate (picture) for wall mounting?

I attached a plastic canvas to a soft Styrofoam panel with nonwoven wallpaper adhesive. It hero. What didn't hold was the wall mounting. I attached a thumbtack to the plate with UHU all-purpose glue and then another 5cm wide layer of UHU and finally fabric tape over that and then attached the plate to the…