To create a toast notification in Flutter, follow these steps:
- Add the fluttertoast package to your pubspec.yaml file and run flutter pub get.
 
- Import the package in your Dart file: import 'package:fluttertoast/fluttertoast.dart';
 
- Call the Fluttertoast.showToast() method with the desired parameters, such as message, length, gravity, background color, text color, and font size.
 
Example code:
Fluttertoast.showToast(
  msg: "Hello, world!",
  toastLength: Toast.LENGTH_SHORT,
  gravity: ToastGravity.BOTTOM,
  backgroundColor: Colors.grey[600],
  textColor: Colors.white,
  fontSize: 16.0,
);