How to Create a Web App To Create Real Looking Product Mockups?

Hello everyone,

I want to build a web app similar to the online mockup generator tools out there like this one.

I have a rough idea of the product, but I’m still figuring out the technical side of things and not sure what the best place to start would be.

If anyone has experience building something similar, I’d love to hear your suggestions on the tech stack, rendering process, or overall approach.

Any help would be appreciated.