This flash is support for teammates peeking top mid from window. Its role is to make it more challenging for TTs contesting the window teammate.
Considered essential for regular rounds, this flash should be thrown every round by the second A spawn (the second player closest to A Site), while the first spawn is supposed to throw this molotov.
Technique:
It's loose lineup, just don't hit wall, there is no perfect way to throw this; shown one is example.