You've successfully built a Flutter app and are ready to release it on the App Store and Google Play. First, you need to set up your Apple Developer account and create a unique bundle ID for your app, then register it with App Store Connect. Next, update your Xcode project settings to prepare your app for release, including adjusting the iOS Deployment Target and signing configuration. After that, build and upload your app to the App Store, where it will be reviewed before release. On the other hand, to publish a Flutter app on Google Play, you need to add a digital signature, create a keystore, configure signing in Gradle, review the app manifest, and then build and upload the APK to the Google Play Store. Throughout these steps, ensure that your app meets the necessary requirements and guidelines for release.