It certainly depends on what's your definition of "easy".
If you're coming with no experience in programming at all, nothing will be easy. There might be tools which focus on one programming language, but they would abstract away too much details of how web based apps work in general to really understand what you're doing.
If you have some experience in a programming language or coming from just another field than web development, I'd suggest you go with a web framework which is commonly used in your programming language's universe. That might be Django for Python, ASP.NET for C#, etc.
Your idea with the static site generators could also work. Keep in mind that you're going to create mostly frontend code when using this approach. That involves JS and npm – so you might go deep into the rabbit holes of front end web development, which can be huge. However, if that's what you want, I'd suggest using NextJS over Gatsby since I'd consider it easier to setup for beginners. Using a non-JS static site gen would contradict your "no multiple languages" requirement ;)
I just started to share my knowledge I have as a developer and trainer, so there is not much to see here, yet. I think the best article so far has been the one about slicing (it got a huge traffic spike from reddit): https://bas.codes/posts/python-slicing
I would love to hear feedback to improve my writing.