Simplified steps to amend the template

cd react-native-scripts/
yarn cache clean --pattern react-native-scripts
npm run build
yarn pack
rename output file to react-native-scripts.tgz
cd your-project-directory
create-react-native-app your-app --scripts-version your-project-directory/create-react-native-app/react-native-scripts/react-native-scripts.tgz

Detailed steps

Please refer to CONTRIBUTING.md