Sitting form and related stretches to improve

I've always been a generally active person, but ever since COVID, I generally WFH, and I find myself sitting a lot(Like 10+ hours a day). I've gotten better in trying to get myself up to walk every few hours, but I think the excessive sitting has really made my legs and hips get tight.

Inspired by some posts on here, I started incorporating weighted barbell good mornings into my workouts, and I'm now starting to realize I might be sitting improperly. I've always gotten a bit sore after sitting for some time, but I'm a pretty slim guy, so I assumed that was just my bony butt.

Ever since the good mornings, I can kind of feel that I'm sitting in a better position, so I'm curious if anyone has any suggestions for similar exercises/stretches that would improve my leg/hip flexibility and any suggestions for mini stretches I can do throughout the day as I have to sit a lot for work.