Do this
Wet your hands and rub on a pinch of salt. Cup one hand into a V. Press the rice with the other palm. Turn it a third and press again, 3 times in all.
Why it works
Each press sets one corner of the triangle. Three short presses fix the shape. The grains inside never get crushed.
When to skip it
Skip it for round or barrel shapes. Roll the rice gently between both palms instead.