In the course of training, you may take the dog with a leash, point at a chair, a table or a box and say "put your hands on" to him. Perhaps the dog will jump on the box, if so, pull him back, you must help him put him feet on the box, and give him a command "stay". If the dog want to sit down with his forefoot on the box, you should teach him a correct posture, let him stand up straight! when he does well, say "good" to him and feed him a little delicious food as reward.

Now, you can add the word "box" in your command, ask him to put his feet on the box, as well, you can add other objects in your command gradually, such as putting your feet on bed, chair, bench, table and so on, your dog will distinguish them soon.