How long did it take to set up a portable runway? How long did it take to set up those metal runways? Were the metal sheets spiked into the ground? How big were they? Also, how are commercial runways built?
Google is your friend. Try it. "perforated metal airstrip" 

https://en.wikipedia.org/wiki/Marston_Mat

"A runway two hundred feet wide and 5000 feet (1500 m) long could be created within two days by a small team of engineers."