"If you don't mind, could please tell me how do you lie down and work ?"

I have three "workstations" at my office - two of them take place at my adjustable height desk. I can stand or sit.

I also have a full sized couch that I can lie flat on. I prop my laptop up on a pillow just like you might at home.

I move between these three positions as it suits me and can avoid completely any kind of fatigue or unhealthy postures.