Wow, check out this guy who’s drawn many 3D holograms by hand. I guess it’s just matter of some angles and hand work. It’s amazing work of art and might be a great example for future college classes on optics.
Scratch-holograms can be made on CD cases using a couple of thumbtacks poked through a stick. Or get fancy and use a professional compass and black painted polycarbonate. Or automate the process with a paperclip stuck into a motorized electric eraser.