By slowly increasing the level of distraction and distance from your dog, you can create a super-effective verbal sit command that works anywhere, anytime.
A reliable sit-command that works anywhere and anytime, at a distance and with distractions, is the most valuable tool in training. But training is very context dependent, so it takes a lot of practice.
Introduce distance commands slowly, and don’t push your dog too hard too fast. Maintain a level of training which is challenging, but allows your dog to succeed the majority of the time.
Teaching distance commands can take a lot of focus. You need to concentrate on the dog, and you may need a lot of energy to keep their attention from farther away.
If you challenge your dog too much, they may go floppy on you. This position of helplessness means you need to be gentle with them. Getting angry will only further encourage their submissive posture.
Practice your distance sits while your dog is roaming, sniffing, and not paying particular attention to you. If you’re in an unconfined place, you can practice with a very long leash.