As soon as he gets it right, we start counting. We do it enough times in a row that he stops relying on his brain to tell him what to do and instead trusts his body to remember how it’s done. (The amount of times you should repeat this varies from person to person. It can be anywhere from 10 times to 30+.)
Together, we then work on tricking his brain into avoiding exactly that by focusing on training his body. With the board laying flat on the sand, I have him simulate the action of standing up on his surfboard with the correct position, in one motion.
This is one of my favorite techniques to accelerate my learning curve in any activity especially if it involves physical skills. Fast learners take the plunge and go all the way. They harbor the crazy hope that they might get it right on the first try.