This way of calling the dog to you it is possible to train only in the time, when the dog absolutely knows the command "heel" with connection of walking next to you. But let's explain the whole thing straight, when we speak about calling the dog back to us.
The whole trick looks like this. The master goes forward, with the dog following him next to his leg, then he puts the dog off leash and on the command "free" the dog has to go away at least to distance of 10 steps from the master (after running away to the showed way the dog can freely move on the area). The master continues to walk and later he calls the dog back with the command "heel". The dog is supposed to come back fastly and the shortest way and straight to the leg of the master to join him in the walk. After few more steps (on the command of referee) the two stops and the dog sits next to the leg of the master, after getting the command "sit down" or "heel". Approved commands are the name of the dog, command "heel" and the gesture of slapping your leg with your left hand.
During training this, I recommend to use the long leash. To work with it is similar like at the command "come here", only the whole thing is trained during walking. Of course, you keep in your other hand some reward or toy, which you give the dog straight after joining you at your left leg. Don't forget to praise the dog.

The dog goes next to leg of the master (starting position).	The command "free !".	After the command dog runs away.
The master gives the command "heel !".	The dog arrives and joins at the left leg.	The command "heel !" (or "sit down !").

I wish you lots of strong nerves and patience. Next time, we will discuss the problem of dog walking next to our leg.

Helena