When you’re building frontends, there are existing frameworks which can help you quickly build usable and accessible services.
GOV.UK Frontend has layouts, styles and templates you can use. Even if you are not using GOV.UK branding, you can use the unbranded templates and build on top of a solid foundation.
The GOV.UK Design System is a repository of all the common components and patterns. If you’re using GOV.UK Frontend then the Design System components will work without installing anything additional. The components are available in HTML and Nunjucks markup.
DWP CASA is a NodeJS framework built and maintained by DWP Engineering. It ships with GOV.UK Frontend built in and will give you additional features such as routing logic, validation helpers, session management and protection against common security vulnerabilities. If you’re building a NodeJS project in DWP, it is recommended you use the DWP CASA framework.
By using these resources you will leverage a lot of best practices and research on accessibility automatically.
For more in-depth accessibility considerations when building frontends you should read the Software Engineer or Frontend Developer guidance.