What are the most popular poses of the last three people in the dance?

That depends on what kind of dance it is. If the folk dance is generally high in the middle and low on both sides, or one high and one low is layered in the middle. You can also kneel on the ground in front, and the other two are back to back, lifting your legs and pulling your legs. If it's a modern dance, I think it's entirely possible to stand in a diagonal line with one person. It doesn't cost anything to get together.