Start from the Buttons (no page by this name yet) page and keep what it gives you: a real button element, a visible Focus ring (no page by this name yet), and a label.
- Give an icon-only button an accessible name.
- Keep label and background to the contrast in Check text contrast.
- Don't remove the outline; restyle it if you must.
If a term here is new to you, look it up in the glossary.