Crosscut one end of the board at a 45 degree angle, beginning the cut in one of the corners.
Draw a pencil line parallel to the 45 degree cut 4 inches up from the sawed edge.
Raise the table saw blade to the maximum height and position the rip fence 1/4 inch from the blade.
Press the longest edge of the board tightly against the rip fence and make a cut up to the point where it meets the pencil line.
Stop the saw and adjust the rip fence to 5/8 inch and repeat the process, again cutting up to the pencil line.
Repeat the process, moving the rip fence 3/8 inch farther from the blade with each cut, until you reach the other edge of the board.