6' Lead w/ choke chain. Walk forward with the dog following you, tug a few times if he is lagging behind. Stop, say Sit, tug straight up on the chain. Don't be hard on him, obviously he needs some teaching first.
Not sure if thats what you are asking, but thats how i'd make sure my dog was in position and sitting when I told him to.
Smartworks, Fowl Dawgs, Total Retriever Training, or for 25 bucks you can get started w/ Duck Dog Basics 1. Among others.
First time trainer here.
Found a clip for you -https://www.youtube.com/watch?v=ZHoMpP9Rubs
@ 1:00 mark