My portfolio page is created using posts and is not a static page like the About page. I did this to easily add and remove entries and so that the page didn’t become too large. It will display a set number of entries like any other blog post page.
The portfolio entries are in the category, portfolio. The code on the portfolio is set to only display that category.
I also use the Ultimate Category Excluder plugin so that the category does not display in my archives or in my rss feed. I’m hoping to spend some time on code based solution for that as well.