There are a few clues as to the location of the action of this poem. Since Maru Mori is Chilean (more on her in "Shout-Outs"), and so is the poet, we can jump to the wild conclusion that these socks are keeping Chilean feet warm. We also know that both Maru and Neruda lived in the twentieth century, which indicates that this poem is likely set in a contemporary time (it was written in the 1950s).
So, a little detective work can help fill in the background, but where is this poem taking place in the poem? That's a bit harder question to answer. If you think about it, what's the place you're most likely to put on socks? Right! The kitchen. Those grapes aren't going to stomp themselves, right?
Hah? No? Oh, well fine then, Shmoopers. You can put your socks on in the bedroom if you like. It sounds crazy to us, but we'll try anything once! So, if we're in the speaker's bedroom, trying on these maginificent socks, that would put us in a cozy, personal, intimate space. If we wanted to take that idea further still, we could take our cues from the wild imagination of the speaker as he likely sits on the bed, checking out the socks—which become fish, sharks, cannons, blackbirds, and a bunch of other things.
And so, while the focus of the poem is on these transformations—and not on the physical details of the setting—it might be most accurate to say that the setting of this poem is really in the speaker's mind. In other words, it is through his imagination that we learn all about these super-cool… foot accessories (we're running out of sock synonyms!). That makes good sense, too, since one purpose of this poem is to underline a way of looking at—and appreciating—the world around us (even under our feet!).