This one is super simple because dogs understand boundaries. I chose this line.
Most people won't have to try to get the dog in the kitchen with them, but your dog being in the kitchen with you is the first step.
Walk toward your dog so he has to back up past the line you decided on. I say OUT and the same time.
Once he is back past your predetermined line, give him a treat! It will only take a few repetitions for the dog to get it.
Make sure you're consistent! This is one where even one person in the household slips up, the dog can regress in progress.
I allow my dog to come into the kitchen to clean up spills by invitation only. I say "Maslow, come and get it" and that's the only time he is allowed in.
What the whole motion looks like.
Be sure to check back for more training and be sure to follow!!