https://www.healthline.com/health/fitness/superman-exercise
https://m.youtube.com/watch?v=CfiJ4qfaUbM
And get a foam roller for a easy low back massage.
I used to have low back pain for a long time from too much desk work. Although I do a lot of different exercises now, I think those 3 things are the easiest and most impactful way you can keep yourself pain free. They're simple, 5 or 10 min a day will really help.