1993 fat boy Seat height: 673 mm (26.5 inches) If adjustable, lowest setting. 26 inch is pretty low compare to many. A seat like came on 1996 would lower it a good bit.
Your options are as follows, get the seat modified, get a different seat, lower the bike or a combination of seat and lowering. Not a whole lot of options but you can likely get it as low as 21" with the right combination of seat and bike lowering, but you would likely be looking at about 1-2" ground clearance at the frame if you went that far.