Some people have a wooden board secured in the car, with a roof rack's front fork holder. So the bike is standing up, just like on the roof.
This is good if you are transporting more than one bike. You'd still need to remove the seatpost if it's too tall to fit.

Rear wheel removed: The derailleur hangs down below the frame. A front fork roof clamp is too narrow. You could make a short stand out of a cheap quick release and a discarded rear hub from the LBS junk bin, strapped to a block of wood to raise it high enough to keep the derailleur off the floor.


Laying it down
My bike lays on the left side with both wheels on. So there's no setup needed when I arrive. I've already pumped the tires, so I just pull out the bike and go.

The bike rests on the end of the handlebar and the bottom of the front wheel, the saddle, the left pedal, and the rear quick release. The frame never touches.

I have a couple of squares of that grippy shelf liner that I fold and put under the pedal and quick release, mostly to keep the bike from sliding around.