Where is Dart's SDK located within /flutter folder?

The Dart SDK lives inside the bin/cache/dart-sdk folder of the Flutter SDK. It will be downloaded the first time you run the flutter command, so may not exist if you've not yet run flutter.

The Dart's SDK is located at /flutter/bin/cache/dart-sdk

However, If Android Studio's flutter plugin is installed, the plugin needs to be told where flutter's SDK is located. Android Studio should be able to locate Dart's SDK afterwards: