Not answering your question I'm afraid. But WHY? If you want to create your own custom page, why not use UIBUILDER which will give you a lot more control and less hassle?
I should check ui-builder probably, I found it a bit confusing so far, currently I am using the template because in the template I can stream live data from the flow and get inputs in the flow from template.
You can create a static page for your basic stuff and then you have multiple ways to send updates depending on your needs and your preferred way of working and experience.
Happy to help if you like. But there is also a walkthrough in the docs and a similar walkthrough on YouTube that should get you up and running at least with an example page.