Deeply unofficial Spaceteam card game timer app
For the most part, this is a very standard Flutter app and all of the standard info in those docs should get you most of the way there.
If you change the icon (see assets/icon/icon.png) then re-run flutter packages pub run flutter_launcher_icons:main to get the new iOS/Android icons.
To make a new Android release, create a file called key.properties in android with the following content (replacing all the "my" items as per https://flutter.io/docs/deployment/android#reference-the-keystore-from-the-app)
storePassword=myStorePassword
keyPassword=mykeyPassword
keyAlias=myKeyAlias
storeFile=myStoreFileLocation
Run flutter build apk --release to generate the file in build/app/outputs/apk/release/app-release.apk
TBD. The Travis builds check that iOS at least builds, but a lack of an iOS device and my unwillingness to give Apple another $99/year means I haven't tried this out yet.