Nonchalantly, Harry pulled a tiny black-plastic bag from his pocket and (wandlessly and wordlessly) enlarged it. Harry hit Riddle’s severed head with a Stasis Charm, put the severed head inside the black-plastic bag, drew the drawstrings tight and tied the drawstrings together, shrank the black-plastic bag (and the head inside the bag) down to tiny size, and put the shrunken bag back in his pocket.