[colanderman]

Making a habit of periodically mentally visiting your limbs and back can help. I don't regularly practice meditation but I believe it relates to this.

But I think best is to set yourself up for success. Make proper posture the easiest option your unconscious brain has. If there's something you're slouching on, remove it.

As I mentioned elsewhere, I have no chair back or arms, since I would always slouch on them. They're gone, no more slouching on them; I spent more time by default just sitting upright. Now I slouch on my desk though; I should figure out how to remove it from the equation.