I use a couple of folded up pieces of grippy shelf liner to help keep my bike from sliding around. It's laying on the non-drive side. I put a piece under the rear hub and another under the pedal. ( the remaining contact points are the saddle and the end of the drop bars and the front wheel.)

The shelf liner also keeps cardboard boxes from sliding, so the pieces stay in the car.

My bike fits without removing the front wheel. It's nice to not have to deal with reattaching it and checking that the brake pads are spaced correctly.