Could someone explain the dragon's hitbox so I don't make the same mistake again? When the dragon is perched in the middle, and you are trying to do the bed technique in the bedrock tub, sometimes you take damage from the dragon. Why does this happen? And what could we do to prevent it from happening?

If you let the dragon fly too low, it can hit you. I recommend you press F3 + B to see all hitboxes, and study the dragons hitbox yourself, and find the sweet spot for when to explode the bed, and how low to let the dragon purge.

Sorry I should have been more specific. I can see how that could happen if you are one-cycling the dragon. But I'm just talking about once the dragon is fully stationary in the middle. Just trying to 'bed the dragon' that way. The problem is, sometimes you can damage it just fine, but other times when I'm doing nothing different, I'm getting slain by the dragon.

then find the spot to stand every time to not get hit

Yea that helps a lot thanks

There are two main ways u can take damage from the dragon when you are in the middle. The first one, being more common is dragon breath. Sometimes, dragon breath is able to reach you even when you are positioned in the middle. The way you can prevent this is just to stay away from that breath and not touch it. You'll still be able to place the bed under the dragon's head so just keep that in mind (you may use f3+b to see where the damage hitbox of the dragon breath and avoid it). Another way you can take damage is if you decide to jump and your hitbox hits the dragon's hitbox. The way to avoid this... don't jump.. at all. One last reason is ur bed explosion. Sometimes, your bed explosion may launch u a bit into the air, added by fire damage may be enough to launch u into the dragon's hitbox. To avoid this, u need to have proper bed placement. This video will help u on that. However, I do recommend u begin to learn one cycling than to use the original strategy

Thank you for the tips. I actually do know how to one-cycle the dragon. The thing was, I had a run where the dragon perched early so I didn't have an opportunity to one-cycle. So instead I did the second fastest thing, which was the original strategy. But died lol. So I was just wondering what I was doing wrong. Thanks for the input though this really helps.