Join the four pieces together using tape or glue at the edges to form a pyramid shape.

Set your phone screen brightness to 100%.

Trace the trapezoid stencil onto the transparent plastic four times. Cut out all four pieces.

For more advanced, permanent holograms, you can use specialized LitiHolo hologram kits , which utilize lasers and specialized film. If you tell me:

On graph paper, draw a trapezoid with these dimensions for a standard phone: Base 6 cm, Top 1 cm, Height 3.5 cm.

Search YouTube for "3D hologram video" on your phone. These videos usually feature four identical images on a black background.

Turn off the lights for the best effect, and watch the 3D image float. Pro-Tips for Better Visuals: