I need to sit down and work it out on paper, but as a long standing reverse parking fan - I can't park forwards, as it's too difficult - I don't think the diagram shown here is quite right. When going backwards at low speeds, the fact there are two rear wheels is very important! When reversing when turning fully left, the left rear wheel stays pretty much where it is; when reversing when turning fully right, the right rear wheel behaves that way.

OK - well, this is of course not quite true, because the car is moving, and so it's not quite rotating around a fixed point. But it's close enough that you can pretty much start your reverse parking manoeuvre by putting one wheel in the right place, so its contact point is lined up with wherever it ultimately needs to be - but it doesn't really matter which angle, provided it's within 45° or so. Then turn full lock in that direction (left for left wheel, right for right wheel), on the spot, and slowly reverse until the other wheel is lined up too.

Now you're done. Straighten the front wheels and go in backwards.

It's handy to bear in mind the swept volume, as there will be some overhang, but when going in backwards with this technique you don't typically have to worry about it too much.

(Making the wheels turn on the spot is not the best thing, but you can fix this once you're confident with the basic manouevre.)