You could shape it with the clicker. If he puts his foot even close to what you're looking for, c/t. It will take many reps before he makes a connection. Or you can just cross his feet for him and c/t. Once he's doing it when you use your hand signal, put a cue to it. Your hand signal will be something like what your hand is doing when you touch the side of his foot just as you're about to move it over. Try to eliminate touching him asap and get him to do it by himself. Don't talk much at first. Let him concentrate on the manuver itself before you start adding a cue.