I need help with some ideas on how to make licorice stay in the shape of a rainbow. Thanks for the help.

Run wire through the center?

I had difficulty too when I wanted to use red thin licorice for hair! In fact I didn't wind up using it in a 3d version, except for bangs but had more luck when I did it on a cut up sheet cake made into a girl. For a rainbow would u consider backing it with a gum paste or fondant cutout so that u could use royal icing to stick the icing to the "board" and then when dry it should stay. Good luck!