This is probably the set of stretches that I do the most. Before a sit, after, and during really long sits when or if any body parts tighten up. You don't have to be in full lotus, it can be any cross leg posture, or even any combination of legs extended. Once you have a basic repertoire of qigong moves and yoga stretches, they're all weapons in your arsenal and you should use any combination, simultaneously, to do whatever your body tells you it needs to get loose and comfortable.
I spend about 3 minutes on the video to demo, but really you want to take as long as you need to get comfortable.
Now what you can't see in the video, there's a lot of subtle movement and stretching in the frames where it looks like I'm still, that I'm actually doing lots of subtle stretches with all my body parts, like an octopus. Even if I filmed in 4k HD you wouldn't see it easily. It's something you have to consciously on doing, and you'll know if you're doing it right because when you hit the sweet spots on stretches, it kicks in endorphins and pleasure chemicals. It's on the edge between too loose and somewhat challenging stretch (but not to the point of pain).