Most behaviours are taught when the dog is facing and looking at the owner. However, the sit cue should also be taught when he is by your side. Otherwise, when you are walking with your dog and then stop, he is likely to want to step out and then turn to face you. This can be an annoying habit when you want to start walking again and your dog is blocking your path!
You may need to introduce this gradually to your dog if he insists on always facing you. You will want to use your right hand and work towards your dog sitting on your left side.
Imagine the face of a clock. Your dog is at 12 o’clock facing you at 6 o’clock. Ask your dog to sit using the visual cue. Reward when he is successful. Now, keep your dog at the same 12 o’clock position. Move slightly towards 7 o’clock while facing straight ahead towards 1 o’clock. Use the same visual cue and reward. Keep repeating the visual cue as you move around the clock until both you and your dog are facing the same direction!
Repeat this exercise with your left hand and moving so that your dog is on your right side.