SAFE_SLOTS = 1
LAST_FILLER_SLOT = 8
SLOT_COUNT = 16

function selectFiller()
  for slot = SAFE_SLOTS + 1, SLOT_COUNT do
    turtle.select(slot)
    if turtle.compareTo(2) and turtle.getItemCount() > 1 then
      return
    end
  end
end

function placeFiller(direction)
  if direction == nil then
    direction = ''
  end

  while turtle['detect' .. direction]() do
    turtle['dig' .. direction]()
  end
  selectFiller()
  turtle['place' .. direction]()
end

function buildLayer(width, height)
  for i = 1, 4 do
    for x = 1, width do
        placeFiller('Down')
        turtle.forward()
    end
    turtle.turnRight()
  end

  turtle.up()

  dropNonFuel()
end

for i = 1,24 do
  buildLayer(5, 5)
end