This two-part workshop will cover key considerations and best practices when creating a theme for OJS. The first part will show you how to get started creating a child theme to modify another theme’s HTML and CSS code. In the second part, I will share my tried and tested techniques to build maintainable, performant themes. We’ll cover good ways to load custom data, create new pages, organise your code, and use modern build tools like Vite. It is assumes that the participants are able to get OJS running in a development environment and know how to open the application’s code in an editor like Visual Studio Code.