How do you make a hover craft?

At a science fair thing at the mall they made a hovercraft using a 3x3 wooden circle with a hole, a leaf blower goes into the hole which produces thrust. This is only for people around the age of 8 and under, for people around 10+ you should use 2 leaf blowers. I DO NOT recommend this for people 18+ because it may be unsafe due to the weight.