My situation is the same as yours, with a flat face.

After coming to Korea, I began to learn makeup, and I should pay attention to the key points of flat face makeup.

A simple highlight on the nose will be more stereoscopic, and pay more attention to the shadow of makeup.

The protruding part is brighter. If the neck is short, wear collarless clothes. Try to tie up your hair.

It doesn't matter whether the mouth shape is good or not, lipstick can cover most of it.