How To Update A Custom GitHub Pages With Create-react-app As Root

Hello I have read many docs online on connecting gh-pages with create-react-app. But most guides either assume that one does not already have a github pages set up, and that the react app is to be hosted as a directory (ie. username.github.io/react-app) instead of the homepage/root (username.github.io). I am hoping someone can help me out:

1. I have an existing repo for a github pages custom domain. It is currently hosting an older site I built with gulp and static html/css/js, and a CNAME file for custom url.

2. I built a new website redesign with create-react-app in a separate repo (It uses react-router for multiple pages).

3. I want to overwrite the contents of my old github pages site with my new create-react-app website as the root homepage.

Is this possible? If so, what is the best way to achieve this? Thanks

1. In the existing Github Pages app, remove the CNAME and/or delete master branch. Deleting master branch will remove the site, while deleting CNAME will clear up the custom domain back to default [username].github.io.

2. In create-react-app, add CNAME to /public folder.

3. In create-react-app, add line "homepage":"./" to package.json.
4. In create-react-app, run npm run build then run gh-pages -d build build process, then run npm run deploy