Sit and stand are two very different exercises.
Sit is easily taught by holding the foodbowl infront of the dog - showing it theres food in there, then lead the bowl over the pups head til the pups bum touches the floor. Followed by the command sit.

Stand can be difficult for some to teach - not for the dog to learn. A way I like to do it is to use shaping. This means putting the command on while the dog is doing what its supposed to do on its own - but yet without knowing.

Dogs stand all the time. And when it does, you put your chosen command on and praise it. Its a matter of very few sessions before the dog connects the command to the exercise.

Then you can add to the exercises, leave the dog while it sit/stands but remember to go slow. The first meter is always the toughest one. Then its a piece of cake really