Elsinore
The second act makes use of some of Shakespeare’s original lines in Hamlet, with which it soon becomes obvious Stoppard’s play is dovetailing. However, Stoppard never makes the location clear (just as Shakespeare, with minimal stage directions, never makes his locations clear for Hamlet).
Ship. Apparent setting for act 3. Even more curious than the first two acts, this act is apparently set on a ship at sea–an inference the audience draws from the sound effects suggested by Stoppard, such as “soft sea sounds” and “ship timbers, wind in the rigging.” There are three large barrels on the deck (sufficient to hold one or two actors), and a few steps lead to an upper deck. Rosencrantz and Guildenstern are taking Hamlet to England after the death of Polonius, perhaps. But at one point all the traveling players emerge from one of the barrels, and at the end of the play it is clear that the setting is, magically, not a ship but the Danish court.
Perhaps one is meant to assume (from the title) that the play is posthumous, with all the characters dead throughout, not just killed at the end of act 3.