Want to throw someone? You’ve got to get them off balance first. One way to do it is to get them to shift more of their weight to one leg than the other. Now that you’ve got them leaning majority to one side, use your heel to kick the back of their knee – buckle the support.
While you’re setting up all that, use a hand to push their head diagonally away from that supporting leg. This will make it much more difficult for them to resist the action.
Hook the knee, push their face away… or, like the title says – give them the crossface and the hook.