He grins behind Ianto at the characteristic clearing of his desk - not that he blames him because after all lying on decanters and desk tidies does not make for a comfortable fuck. Jack never has been one to have a clear desk. He likes his paraphernalia close at hand.
He doesn't order Ianto to bend over, not in words; he doesn't need to. He just places a large, warm hand in the small of Ianto's back and presses lightly, knowing he'll go over. He leans over him as he goes, to ask, low and alluring, "Do you need me to open you up, or has Spike already done that for me?"
This being a dream, after all, it could go either way.