Here’s something quick I threw together: GitHub - jderochervlk/rescript-parcel-no-framework: A simple example of a webapp using Parcel with no framework, just WebAPIs.
I’m using Parcel as the build tool: https://parceljs.org/
It loads in an HTML file with CSS and JS and does hot reloading on file changes, and it does a good job of bundling including code splitting.
Since I’m not using a framework, I set up a main index.res file that loads in and uses pattern matching on location.pathname and depending on the path it lazy imports a different modules render function. That function replaces the html inside of #main with that page.
It’s pretty basic, but it does use the new experimental webapis and might be an interesting starting point if you want to poke around at a really basic app that doesn’t have a framework.