General UX
Taking a11y into consideration in the design phase goes a long way in setting up the foundations for an accessible site. A clean, clear, and simple to use design impacts all users of the site.
Typography
Fonts and spacing are some of the most important building blocks of a site. There are countless fonts available to choose from, but not all are created equal from an accessibility viewpoint. Choosing a proper font allows for easier reading for all users, not just those with visual impairments.
Color and Contrast
This is another one of the important building blocks. As with fonts there are an almost limitless number of options and combinations available, but it is important to narrow down choices that will allow for easier reading and understanding.
Layout
Hierarchy and order are also important, and should be intentionally used to allow users to discern information as quickly as possible. Reading order and tab order should match the visual order of the page.
Repetition
Consider using a design system that will allow you to componentize the elements needed to build the site, and re-use components as much as possible. The familiarity with the components on the site makes its use much more intuitive to all users.