The strips are narrow enough to bend sideways. As an example... You start on the right side and ad a strip. Then add one to the left side. By going back and forth the stresses of the layup are equalized and the wood strips are "mixed up" so in the end it is stronger than the original piece of wood.
It took me about 30 minutes to lay up the area behind the firewall of the CAP in my avatar. That is after I figured out how to do it
That was my first attempt at strip planking. I'm sure it will only get better.