This creates a perfect opportunity to hug for a few minutes and be intimate. Sitting on top of each other and maintaining stability is a formidable task for most people. Some people prefer facing the same direction. This is preferable for those who feel less coordinated or embarrassed. You do not have to face the other person.
Sex is funny.
Great chairs include rocking chairs, kitchen table chairs and, of course, the chair in the office. Sex on a chair makes for a good study-break. In the ideal world, both people would be of similar heights, or one person could be strong enough to lift the other person to reach the right level. Women need to tilt their pelvic, so that the vagina is forward, and easier to access. However, if the woman is taller, then her partner may need to stand on the small stool.