Dice choose the wall and the break point.
After the four walls are built, East rolls two dice and adds the total. That same total does two jobs: it chooses which player’s wall is broken, and it chooses the exact break point in that wall.
Count players in counter-clockwise order starting from East as the first seat: East, South, West, North, East, South, West, etc. Keep going until you reach the number shown on the dice. This seat which you landed on is the wall which will be broken at.
Once the wall is selected, count that number of stacks from the selected player’s right end of their wall. Count stacks, not individual tiles. Break immediately after the counted stack, then dealing begins from the break.