Has anyone figured out an elegant way to add front-end design to a process like this? Every implementation I see people use includes either vague references to front-end frameworks, or figma images. It doesn't feel like a cohesive design solution.

I have a folder of scss files containing the utility classes and custom properties that make up the design. By instructing it to use those, and to reference similar files, it more or less conforms nicely to the existing design language.