1. Pick the sakura cherry leaves while they are still young and tender (large ones work best) along with about 1~2 cm of their stems, and clean them well by rinsing in water.
2. Drain the leaves, and pat them dry. Place them in a sieve and pour boiling water over them.
3. Quickly place the leaves in very cold water to prevent further cooking or change in color.
4. Drain the leaves again and remove excess moisture by patting dry or using one of those plastic spinners you use to remove excess moisture from lettuce leaves.
5. Lay the leaves out on paper towels or a tray and separate them into groups of similar-sized leaves.
6. Sprinkle 1/3 of your salt over the bottom of a glass cake pan (or round plastic storage container). Divide up the leaves into groups of ten leaves of roughly the same size, and stack them on top of each other in the same direction. Lay the stacks in the pan on top of the salt, preferably without overlapping one stack with another.
7. Sprinkle the rest of the salt over the top of the leaves, and pour the white plum vinegar around and in between the stacks of leaves.
8. Place plastic wrap over the leaves. Then lay a flat lid or dish over the wrap, and something heavy, like a clean brick or some cans of soda, on top of the flat lid/dish.