Wash the rice in a colander until the water runs clear. Soak in enough water to cover for 30 minutes.
Heat the oil in the slow cooker set on HIGH. Drain, rinse, and drain rice again. Add the rice to the hot oil and cook, stirring until the rice is well coated with oil and smells toasty, about 5 minutes.
Add the stock all at once, then the salt and cilantro stems. Stir well, cover, turn the cooker to LOW, and cook, 8 to 9 hours or overnight.
To finish the jook, stir it well if it has separated. If you want it thicker, cover, turn cooker to HIGH, and cook for 1 to 1 1/2 more hours, stirring occasionally. Add milk now if you want an extra-creamy porridge.
To serve, sprinkle over chopped cilantro leaves, minced green onions, salty potato chips, or your seasoning sauce of choice.