It appears many people never considered having a seat when they planned their home. Even though it is one of the most important places there and a little bit of comfort and ergonomics can go a long way, not everyone has a nice chair to sit on. My personal preference would be a place outside, under a small tree, but any place with good light and climate is fine; just don't force yourself to sit on your bed. If you always lie down on a couch or fall on your bed when you're looking for some physical rest, you're making it harder to do anything worthwhile. This observation seems obvious — a study with large desk and chair was standard for past generations, but the appeal of chill and casual has created the unreasonable expectation of a comfortable life.
Even if you don't have to do anything all day, there are better options for sitting down than bed or couch. Optimally, you should switch environments for an activity regularly, but please just start with a good chair. Light, air, a warm breeze — it's an obvious design choice.