Tying your ankles is easy. I prefer to put the left ankle in front of the right ankle, because the ankles can be tied tighter in this way. If you tie the ankles next to each other, and you tie them tight, they press against each other on the bone, and this hurts. Moreover, you are still able to move one ankle in front of the other, and then you have too much freedom.
It is also possible not to tie the ankles at all. Be careful using a spreader! I have no experience with this, but it could be very difficult to pick up the keys when your legs are spread, because you cannot lie on the side, and your hands cannot reach the ground.
If you want a hogtie, then it is better to use the second method on the drawing, so that it is easier to reach the end of the chain, and the force is symmetric on both sides.
I use the following materials: