Fill baggie (for my ATC I’ve used a bag approx 2”x3”) with 1 TBSP of hair gel. Zip/Seal baggie closed. Fold mouth of baggie over and tightly secure with tape to help keep hair gel from drying out or leaking.
On inside of the cardstock run red line tape around the edges of image to secure baggie in place. Run additional red line tape to seal ATC closed and hid baggie edges.
ONE STEP FURTHER:
Add food coloring to create any color desired.
Add Glitter for some sparkle.