Paste the slot HTML directly in the index.html file of your react project. as we did in this project to integrate the slot with dimension 300x250
For adding script as the part of component, you can use the componentDidMount() lifecycle of React. using the document object of browser. for code snippet you can refer to file scriptTag.js in src folder.
You can use the npm 'Helmet' for rendering the script in react component in more easier and readable way. for code snippet you can refer to file scriptTag2.js in src folder.