Find a grassy hillside, and a big cardboard box. Flatten out the cardboard box and drag it up the hillside.
Put the cardboard box down on the grass with the smoothest side facing down. Sit on the flattened cardboard box and let gravity do its thing! Woohoo! A few trips down the hill flattens the grass and improves the ride.
It's the Southern/summertime version of the sled or toboggan.