At one time I tried that ages ago. I didn't like it because there was too much of a tendency to hit the surface the strop was lying on and it was more difficult to get the right stropping motion. With a bench strop you can do it because it's a hard surface to begin with and you are elevated of the table. Also you tend to keep it raised at an angle anyway.

In the end it's best to just earn the proper way. It's difficult to unlearn bad habits later on.