How to add Multiple Floating button in Stack Widget in Flutter

You can use the Align widget to position your FloatingActionButton‘s in the Stack.

Stack(
  children: <Widget>[
    Align(
      alignment: Alignment.bottomLeft,
      child: FloatingActionButton(...),
    ),
    Align(
      alignment: Alignment.bottomRight,
      child: FloatingActionButton(...),
    ),
  ],
)

One button uses constant Alignment.bottomLeft for its alignment property and the other one respectively Alignment.bottomRight.