Using Vanilla HTML/CSS for Results Summary Component

I decided to focus on vanilla HTML/CSS since I'm a complete beginner and wanted to practice in understanding the fundamentals before introducing things like Sass into my workflow.

When making the projects, I had a hard time understanding how to break the components into different parts, resulting in me needing to restart the project. Initially, I was trying to tackle different parts of the design all at once which ended up making things really messy. Eventually, I came up with a result by taking it by the outer layer of the design before going into the details, but I definitely feel like I could have made this more efficiently.

My main question is about best practices: how does someone start off their HTML/CSS before building on top of that foundation to create the rest of it?

Thanks!