To work up to these you start with leaning back gradually. When you can "hang back" and see your mat - and feel fairly comfy with your back strenght - then stretch your arms back to land on the floor. You can do it on a thick carpet if you feel fear of the hard-floor. A lot of leg strenght is needed, especially to lift back up. But the back-drop can be done without a lot of strenght if one is fearless enough. But the gradual working on the leaning back will give you a controlled drop back, and you'll gain loads of strenght in the process which serves in other poses as well. Work on coming up with as parallell feet as possible (if they turn out you compress in the lower back... if they turn out alot you might consider working more on the strenght of your spine and legs). This pose is ALOT about the legs. Have fun! Ps: There is a video on this blog, from a couple of years ago, where I show how to work on this drop-back using a wall. Ps.2: check out the demo of "how to work on Press Up Handstand" HERE
In this pose I'm showing how to work up to a Handstand-Press-Up. The first one is an example of how to work up to pressing up into handstand from the floor, with legs united. And at the end there is a video showing an example of floating up with "wide-legs") These are advanced transition. For the "united legs" version - openness in the hamstrings is needed aswell as strong arms/shoulders and some core (especially for the down-float). In this demo I'm using the wall, and pressing my head into it. This is very helpful for working on the "actions" to then press up without a wall. Try working on coming down "with control". You have to be far enough from the wall to be able to lean forward and have room for your spine and buns as you press up - but close enough to be able to press the back of your head into the wall. Also it's pretty crucial to have the feet as close as possible to your hands. Press into your hands firmly and lean forward (leaning the back of the head towards the wall), and the legs will kinda automatically float up. Though - to come down gracefully you need to engage your core alot. If you're too close to the wall or have your feet too far from your hands (it has to be a deep uttanasana), it will not be possible to float up. (your back or buns will touch the wall and hinder the lift up, if you're too close). I'm finding it helpful with a thicker blanket up the wall, since that makes the "wall" come closer to my head as I still have room for the forward-leaning. As soon as you find the right distance from the wall and remember to keep your feet closely before starting - it's a float-up each time. Then work on coming down as gracefully as possible. Have fun! Ps. If you want to try floating up from the floor from Wide-Legged Forward Fold (Prasarita Padottanasana), there is a video of how to work up to that transition using blocks. Check this video below: Ps.2: Here is a video demo of Yoga Drop Backs.