Stand it up straight, and a pair if tie downs to the frame or bars. Then all you need to do is hold the front wheel in place either with a wheel chock or a couple more tie downs. I've hauled my bike on 6 hour drives in the back of my truck a couple times like this with no problems at all.
If you tie to the bars, be careful of the plastics and don't tie to the end of the bars. You could bend the bars that way.