One of the best things is spending time away from your desk, I guess, and making that part of your lifestyle. There is a subset of qigong/chikung that focuses on standing meditation, which is a habit you can pick up for life. Probably helps to have an irl teacher though. I think doing that Foundation Training free vid for a week is the best thing to do right now and if you like it keep at it and/or look into yi chuan/zhan zhuang.