In a detailed tutorial by Anthony Giuliano, readers are guided through building a countdown tracker component using Stencil, an open-source tool for creating reusable web components suitable for integration into various frameworks like React, Angular, and Vue. The tutorial explains how to use Stencil to create a countdown tracker that calculates and displays the time remaining until a specified event, using JavaScript's Date object and functions to manage time conversions and updates. The tutorial emphasizes the use of props to receive user-defined dates and state management to update the countdown dynamically. Additionally, it discusses creating an animation loop using requestAnimationFrame to ensure continuous updates, along with addressing how to stop the loop once the countdown reaches zero. The guide concludes with styling tips to enhance the visual appeal of the component, encouraging developers to incorporate their own styles and explore further component development to build comprehensive design systems.