create a new route in app folder, for example, app/notFound/index.tsx:
import'./style.scss'const NotFound: React.FC=()=>{return(<divclassName="not-found-container"><divclassName="error-code">404</div><divclassName="error-message">Oops! Page not found.</div><divclassName="back-link"><ahref="/home">Back to Home</a></div></div>);};exportdefault NotFound;
create a new style file in app/notFound/style.scss: