Easily found! For you see, I have supplies... for building a deck! [Papyrus gestures expansively at the staircase, gesturing Yakko to join him going down to the garage.] If a platform is just a different sort of deck, we're already halfway there.

[It may not actually be constructible at the speed necessary for the visual gag necessary, but Papyrus doesn't know the nature of the punchline here, and he's just going with it - the better to, presumably, cheer Yakko up about the whole kidnapping and turned human thing. At least they can stand and make puns about the construction supplies.]