Use Flutter Local Notifications library - https://pub.dev/packages/flutter_local_notifications#periodically-show-a-notification-with-a-specified-interval

Periodically show a notification with a specified interval:

const AndroidNotificationDetails androidNotificationDetails =
AndroidNotificationDetails(
    'repeating channel id', 'repeating channel name',
    channelDescription: 'repeating description');
const NotificationDetails notificationDetails =
NotificationDetails(android: androidNotificationDetails);
await flutterLocalNotificationsPlugin.periodicallyShow(0, 'repeating title',
'repeating body', RepeatInterval.everyMinute, notificationDetails,
androidAllowWhileIdle: true);