Heat up your wok, add oil.
When shimmering, add minced garlic.
Fry just for a few seconds until fragrant. You want to make sure that you don't wait too long before adding the garlic to the oil, otherwise, the oil will be too hot and the garlic will burn.
Add your long beans, fry in a wok for 30 seconds, tossing the garlicky oil all over the beans.
Add water, oyster sauce, and soy sauce. Cover the wok. Let the beans steam for 5 minutes on medium heat.
Check to see if beans are almost tender, but not too soft. If not, re-cover and steam an additional 1 minute. Uncover, let the rest of the liquid evaporate, about an additional minute.