As a product person, most often than not you end up iterating a lot over the interaction and use cases for an interface or a set of interfaces on the website.
It is not always possible to figure out and visualize the entire interaction without any visuals in sight. However, it's a good idea to have a skeleton sketched in one's mind and translated in a doc. Which could then be beefed up. This definitely reduces iterations because if there is a structured doc that one has to fill, you end up thinking a tad more than usual.
I just made a rough template that could be used :