Did you know in order to teach stay correctly and quickly you should always return to the dog?
If you don't come back to the dog you're not actually rewarding the dog for staying. A common mistake I see people making is they will ask their dog to stay and then recall it. That won't help your dog learn as fast!
An example of a good stay exercise is:
Have the dog sit.
Walk one pace back.
Return to the dog.
Mark and reward.
Overtime you will be able to get further and further away, and add in distractions and longer lengths of time.
Walk away and come back few times and then release the dog with a terminal marker such as "okay" or "free" or "release." The word doesn't matter as long as you're consistent in your usage.
Using reset treat is really helpful for this!
Throw a treat 10-18 inches away so the dog clearly can see it while simultaneously saying your release word.
The release word will help your dog stay because it lets it know that there is an end to the task!
Did you know you should come back to your dog when teaching stay?
