Find a boss who doesn’t care. So far I’ve never had a boss that insists that I look busy all the time. As long as I’m getting my work done they don’t care what I do. I spend a lot of time at my desk reading books on my phone. If your boss is being an ass about you using your downtime how you want when all of your work is done then that is not someone you want to work for.
It’s not that my boss cares per se, but I still think people form a subconscious image of your work ethic, and I think it’s always better to be seen as a “hard worker” when it comes to promotion time
I worked with a guy that if he slept in or ran late for work tossed his gym gear on instead of his work clothes and ran into the office apologising and went to the bathroom to get changed.
People thought that he was a fitness NUT and he always stayed back to make up the time so he was called dedicated. In truth I knew he trained after work and regularly stayed up mega late playing COD and slept through his alarm.