DigTarget.lua

local function forward()
  while not turtle.forward() do
    turtle.dig()
  end
end

target="minecraft:dirt"
target2="minecraft:grass_block"
lw=8 -- length and width, It'll just be a box


local function digUp()
  local has_block, data = turtle.inspectUp()
  if has_block then
    if data.name == target or data.name == target2 then
      turtle.digUp()
    else
      print("Target=",data.name)
    end
  end
end

function digDown()
  local has_block, data = turtle.inspectDown()
  if has_block then
    if data.name == target or data.name == target2 then
      turtle.digDown()
    else
      print("Target=",data.name)
    end
  end
end

flip=0
depth=3

function flipper(f)
  if f==0 then
    turtle.turnRight()
    forward()
    turtle.turnRight()
    f=1
  else
    turtle.turnLeft()
    f=0
    forward()
    turtle.turnLeft()
  end
  return f
end

for z=1,depth do
  for x=1,lw do
    for y=1,lw do
      digUp()
      digDown()
      forward()
    end
    flip=flipper(flip)
    forward()
  end

  -- flip=flipper(flip)
  if flip==0 then
    flip=1
  else
    flip=0
  end
  for x=1,3 do
    turtle.digDown()
    turtle.down()
  end
end
for x=1,(3*depth) do
  while not turtle.up() do
    turtle.digUp()
  end
end