I have not tried this so not sure if it would work. Could you use a hair dryer on the area that you want to put the design? It was just my first thought when I read this.
I had used tape sticky double side , the quality for carpet, which sticks hard
Hugs
There are several methods but I attach mine by warming a few spots with my Decorative Touch Wand (the mini iron to attach rhine stones etc.) that melts the candle wax and I push the FSL in it. That way they can be easily removed when the candles burns down.
In the case of the angle I fastened the wing tips, the tip of the trumpet and the left and right skirt bottom.
This is also a very lovely candle, now I have to find the special FSL design... thanks again