The next scenario you're giving a briefing to someone in the office or your organization in your seated. Now this can seem easier, you're not standing in front of a whole bunch of people. You're not as self conscious about your body and your hands. But there's still things you need to watch out for. For starters, don't get too comfortable. There's the tendency to think well, it's just seated and you're leaning, you're slumped over, maybe looking at your screen, my recommendation, I want you to be comfortable, but I would still hold myself high, lean forward and not have my hands touching the table.
When talking. If you're listening to someone, by all means, have your hands on the table, but when you're talking gesture, you'll come across more comfortable or confident and relaxed. Too many people put their hands down once you put your hands down, you slump. Everything's all wrinkled, crumpled, looking, nobody looks is good that way. Plus there's less energy in your voice because Cuz you're not moving your hands and your body. The other thing to realize is it still your briefing your presentation, you may want someone to look at a computer screen or maybe you're projecting it or maybe it's a handout.
But you should be looking at the person or persons, your briefing. All the other material that's for them. It's not for you, and it may seem like a lower threshold less scarier thing. You should still practice on video before doing it.