For your dog to start from a standing position, then sit without moving their front legs/paws.
For good even posture in the stand and in the sit.
Start from a stand. I call this position “up.” You can repeat the cue as much as you like, then treat your pup when they stand.
Ask your dog to sit, barely moving your treat hand. If you move it at all, move it ever so slightly horizontally towards your dog.
When your dog sits, reward with another treat.
Try to keep “feeding” your treat hand with your free hand so when you aren’t re-loading when you actually need to reward your dog – which can work as unintentional lures out of position.
If your dog is struggling, focus on Stand to Down until they are really good at that exercise, then revisit this one which is more advanced. And ask Emma if you have trouble of course!