2Ns and a K vs. a K?

I've always understand that it is possible to checkmate a King with two Knights and a King, but only if the lone King blunders by stepping into the checkmating square (a corner square).  Does anyone know whether it is possible for the lone King's blunder to occur one move earlier, so that the King's final move to the checkmating square is forced?  My son has been given a puzzle -- White has two Knights and King, and Black has a King; put the pieces in whatever position you wish so that it's White to move, with a forced checkmate in two.  Possible or impossible?  Thanks for your thoughts about this.

I just don't see how it could be possible.

It's not possible.

There is a mountain of theory concerning when it is possible and when it's not - in the case that Black also has one pawn that's blockaded.  But that's pretty advanced stuff, and such situations are quite rare.

There has to be something else on the board to be possible.(pawn)