Apparently the way it works is to get an offensive player on first, second, AND third at the same time. If the batter then hits a fair ball beyond the boundaries of the playing area, all of the runners INCLUDING THE BATTER get to cross the plate and count as a run scored. A team can do this an unlimited amount of times during a game without penalty.
This is evidently a legal play and has been an option to us each time we've had the bases loaded this season. Another option is to hit a fair ball within the boundaries of the playing area, scoring one, two, or all three of the runners while the batter remains on one of the bases without scoring. Again, there is no penalty for doing any one of these options multiple times within the same game.