Joshua 8:32 reads:
And he wrote there upon the stones a copy of the law of Moses, which he wrote in the presence of the children of Israel. (KJV)
Other translations are very similar.
What exactly did Joshua write?
What was the content of what he wrote? Was it the legal parts of Exodus, all of Leviticus, and all of Deuteronomy? Just the Ten Commandments? Verse 34 seems to indicate that Joshua read what he'd written and refers to a singular "Book of the Law" (capitalized in some translations and not in others).
How do we explain this in terms of plausibility? The context indicates that the nation of Israel was standing there as Joshua "wrote on stones" (chiseled?) the law. I have never chiseled but I have to think it's a very slow process. The text doesn't tell us how long this operation took but I would think that if it's truly "the law of Moses" (all the law?) then it must have taken months...? Did the nation stand there for all this time?
The text does not strictly say that Joshua completed it in one sitting. However, verse 33 is very specific on how the Israelites stood, so either it was done in one sitting or they reassembled precisely each day.