This is the first surf move, the one when you take all the speed you can. All you do during the take off design your next moves on the wave.
During the take off, on a SUP you are stand up. So you just have to move your feet from the paddle stance to the surf stance to do the bottom.
So your feet have to move along the center line of the board. First, the back foot goes to the tail, close to the rail where you want to turn. Then the front foot moves backward but in the middle line of the board to keep the balance. Usually your weight his mostly on your front foot.
But, if the wave is hollow, your front foot will move close to the inside rail to.
The more the wave is powerfull and hollow, the most your stance is wide and you go back to the tail.
SUPer : Patrice Guénolé on a GONG board.

Source : Team GONG SUP.