ionic cordova build android --prod --release
Generate a private key using the keytool command that comes with the Android SDK:
keytool -genkey -v -keystore my-release-key.keystore -alias alias_name -keyalg RSA -keysize 2048 -validity 10000
jarsigner -verbose -sigalg SHA1withRSA -digestalg SHA1 -keystore my-release-key.keystore app-release-unsigned.apk alias_name
zipalign -v 4 app-release-unsigned.apk HelloWorld.apk