To create an interactive web chat experience with Twilio Flex, developers need to set up a Studio Flow that includes four widgets: three Send & Wait For Reply widgets with different interactive elements (buttons, dropdowns, and calendars) and a Send to Flex widget. The Flow should be imported into Twilio Flex WebChat as part of the setup process. Next, developers create a custom React component called Interactives that will handle rendering the interactive elements and sending messages back to Twilio's Chat client. This component includes child components for buttons, dropdowns, and calendars, each with its own logic for handling user input and updating the chat interface. Once the Interactives component is complete, it can be tested by sending a message from Flex WebChat and responding to each of the automated Studio messages, cycling through the different interactive elements and verifying that messages are added to the chat accordingly.