To create a REST API using Flask, you first need to install Flask using pip install flask and then import Flask, jsonify, and request to handle HTTP methods and JSON responses. A Flask app instance is created using app = python, and routes are defined to handle different operations. For example, a GET request can retrieve all users from a predefined list, while another GET request with an ID parameter fetches a specific user. A POST request allows adding a new user by receiving JSON input and appending it to the list, whereas a PUT request updates an existing user’s details, and a DELETE request removes a user based on their ID. These routes process client requests and return responses in JSON format using jsonify(). The API is run using app.run(debug=True), making it accessible at http://127.0.0.1:5000/. Testing can be done using tools like Postman, cURL, or Python’s requests library. For more advanced features, Flask can be extended with Flask-RESTful for structured API development, SQLAlchemy for database integration, and JWT authentication for secure access control, making it a powerful choice for building RESTful services.