Today I make a REAL hoverboard out of dry ice! It doesn’t lift you high into the air like back to the future, but it perfectly emulates the feeling! Its just a wooden board with a rim around the edge to hole 3 blocks of dry-ice in place. As the dry ice sublimates, the pressure from the expanding gas is enough greatly reduce surface friction and you can glide on any smooth surface. The wood floor in this video was far from perfect, but it did the job pretty well! I would consider this a real hoverboard because the dry ice is not in contact with the surface. There is actually a very thin layer of gas between the two surfaces. The problem is any irregularities in the floor surface will contact the dry ice, slowing the board down. If this was on a glass surface, I think air friction would slow you down before the surface friction!
The board can last for an hour before the ice gets too thin. I spent $100 total on dry ice testing, and making this video. each block costs around $15. It works just as well with 2 blocks also!