user13147: With a human vs. computer, simply set Stockfish to depth == 1 and play it. Or, you can choose another (weaker) engine.
With a human vs. human online, is it possible to set the starting position? If so, what is the website?

user13559: You can play it in https://lichess.org/editor.
Chose your default opening, or just customize it, then click in 'Continue from here'.
You can chose if you want to play with with engine or with a friend.

13147: <p>With a human vs. computer, simply set Stockfish to <code>depth == 1</code> and play it. Or, you can choose another (weaker) engine.</p>

<p>With a human vs. human <em>online</em>, is it possible to set the starting position? If so, what is the website?</p>
 13559: <p>You can play it in <a href="https://lichess.org/editor" rel="nofollow noreferrer">https://lichess.org/editor</a>.
Chose your default opening, or just customize it, then click in 'Continue from here'.
You can chose if you want to play with with engine or with a friend.</p>
