In the past I've used a lapboard for this. You can buy fancy ones or build something simple with padding attached to a board/plank. Basically just makes a temp

In the past I've used a lapboard for this. You can buy fancy ones or build something simple with padding attached to a board/plank. Basically just makes a temporary "desktop" on your lap, giving you a flat, somewhat raised surface to place a keyboard and a mousepad. In fairness, I rarely play games with kb/m from the couch anymore, and the arm of the couch (or my leg, etc) are fine for simple things like scrolling on a website with a wireless mouse. But for games or more detailed UIs I still break out the lapboard if I'm using the TV as a monitor.