Export Your Project Code :- In FlutterFlow, export your project by navigating to Settings > Export Code. Download the code as a ZIP file to your local machine.

Edit the index.html File :- Unzip the downloaded project. Navigate to the web directory of your project. Open the index.html file in a text editor or an IDE like VS Code. Paste the HubSpot embed code right before the closing tag.

After adding the code, save the index.html file. Run flutter build web in your terminal to rebuild the web app with the updated index.html.