Open

for i=1,7 do
  turtle.dig()
  turtle.forward()
end
turtle.turnLeft()
turtle.dig()
turtle.forward()
turtle.turnLeft()

for a=1,3 do
  for b=1,6 do
    turtle.dig()
    turtle.forward()
  end
  turtle.turnRight()
  turtle.dig()
  turtle.forward()
  turtle.turnRight()
  for c=1,6 do
    turtle.dig()
    turtle.forward()
  end
  turtle.turnLeft()
  turtle.dig()
  turtle.forward()
  turtle.turnLeft()
end