You don't, you make reusable components in your template language or framework or whatever it is you're using to generate HTML. Most have pretty good support for template re-use and hierarchy and stuff.

In my preferred template language, jinja2, you'd write a macro. https://jinja.palletsprojects.com/en/3.0.x/templates/#macros

Here's how I do it in HTMX with Rails: https://viewcomponent.org/

I used htmx with Clojure and it was easy to mimic components as functions that return hiccup. I have a default middleware that converts it to html before sending it to the client unless I explicitly say it's a json route.

    (defn some-component [{:keys [class]} & children]
      [:div {:class (str "some-component-wrapper" class)}
       [:h1 "Hello World"]
       children])