To build a WhatsApp bot that sends basic stock quote information when a user sends a valid ticker symbol, you'll use the Finnhub.io Stock API and Twilio's Programmable Messaging service. You'll need to set up a Java project using Spring Initializr, create a controller to handle messaging, and start the server with ngrok. Then, you'll create a service class to make requests to the Finnhub API and map the response to a Price object. Finally, you'll format the message nicely in the Controller and test it out by sending a WhatsApp message with a valid stock symbol.