Anywhere man, I think if you’re going to do an extensive hand balancing session on a training day you should do it after your regular training that way you can be as fresh as possible for your main workout. But you can also just work on a skill for a minute or less whenever you find time; sometimes I will do handstands while getting gas. The great thing about it is even if you can only spare literally a minute it’s plenty of time to do these skills; a 1 minute L sit is extremely impressive to me. I can’t do handstands at work because its a “safety hazard”, but I found 1 arm elbow levers a great way to practice balancing and strength simultaneously. Just get creative with it man. Coach Wade, author of Convict Conditioning, recommends practicing flags whenever you’re around a pole on the street!