Considering the various different positions I've bound women in, not to mention all the others I've either seen or heard/read about, singling out three takes a bit of thought, something I try my best to avoid.
Thinking tends to tire my brain, and when both remaining brain cells get worn out, I'm not good for much till they can rest. Anyway, here's the three I came up with:
1. Some variation on a frog tie, like wrists to ankles or ankles to thighs. This position allows easy access to all parts of the body, with a little rolling around, and it also allows for kneeling.
2. Standing spread eagle, preferably away from any wall. This also allows ease of access.
3. Mummification. I don't think any other bondage results in such complete helplessness, especially if you add sensory deprivation by putting pads over the ears before wrapping the head.