I haven’t tried this, but suspect it is more awkward than it looks. Study exactly how they are doing it in porn first and be prepared for lots of laughs is my advice.

Alternatively next time someone is inside you imagine where you would fit the second man and see if that provokes any insight.

The only practical method I can picture in my head right now is missionary (you either way up, and underneath/on top doesn’t matter) with both of you with open legs for someone to stand between. It implies a bed/counter top/table of just the right height though and nothing to support either of you below the crotch. I suppose the standing man could be kneeling, which might be more comfortable. If you work out a way that is genuinely comfortable rather than just good for the camera do let me know.