This is the base of the hovercraft, stained, sanded, and the hole for the leaf blower is allready cut. It was made from the best plywood I could find... 4 ft by 8 ft with the corners cut off...
To build this part of the hovercraft go out and buy a 4x8 ft plywood board, measure 1 foot in from all the corners, draw a line from point to point and saw off the corners.
Next make the leaf blower air feed hole, make sure that at the end the hole's edge is about 2 in away from what you want to be the back of the hovercraft, and make a hole that will accomidate your leaf blower's biggest nozzle attachment.
Sand it
Put a finish on it
viola, you are done...