If you are looking to create a funnel using a one page lander/checkout, then the best way to do it, is to have 'any' page as the official lander and then this 1 page lander/checkout as the checkout page. Then, when you send traffic, you will substitute the /0/ in the URL for /1/
eg.
Instead of:
You can download here the page I used in the video. You will need to unzip it first and import the json file ONE PAGE LANDER CHECKOUT.zip