Separatory flasks that I use have a ground glass joint, but it is not clear how that joint is to be used. Videos I have seen just show people pouring stuff into the throat of the funnel.
Normally the situation I have is that the solution is in a large flask, maybe a 1000ml flask, and I need to separate a thin layer of the solution that is at the bottom of the flask using a 500ml separatory funnel. The question is how to get the bottom of the flask to the funnel.
Saying "oh just use a bigger funnel" is not a solution, because the flasks, reactors and carboys I have tend to be significantly larger than any normal separatory funnel. For example, if I have a 3000ml reactor or 5 gallon carboy with a solution in it, I am not going to go looking around to spend hundreds of dollars on a gigantic separatory funnel.