Most sites allow you to play against yourself, but I don't think I've ever come across a site that will enable you to play an illegal move. Maybe there is some way to do it as well, who knows...
The best way to do this would be on a physical chessboard.
So like I’m trying to play chess with a ai but it keeps making illegal moves which I can’t do so I’m wondering if there’s a website where I can do illegal moves and play by myself