As someone with a sub250kb website (30.45KB), I can recommend to look into HTML templating things. Stuff like Jinja2 or the Go HTML templater. Then you write raw HTML with some CSS.
This also makes my ADHD want me to make a sub 1kB webpage out of what I have atm, though it might be hard considering it includes a 4KB image.
If you need a quick and easy setup, lighttpd will let you serve an HTTP directory listing within 10 minutes. And probably more safely than FTP. With an additional 10 minutes, you can setup certbot to handle certificate rotation.