Two layers

-- 1 - obsidian
-- 2 - quartz

shrek={
      {1,1,1,1,1,1},
      {2,0,0,0,0,1},
      {2,0,0,0,0,0},
      {2,0,0,0,0,1},
      {1,1,1,1,1,1,},
      }
function buildLine (colors)
    for i = 1,#colors do
        slot = colors[i]
        if slot~=0 then
          turtle.select(slot)
          turtle.placeDown()
        end
        turtle.forward()
    end
    turtle.turnRight()
    turtle.forward()
    turtle.turnLeft()
    for e = 1,#colors do
        turtle.back()
    end
end

function buildLayer(image)
    for i=1,#image do
         line=image[i]
         buildLine(line)
    end
  turtle.turnLeft()
 for i=1,#image do
    turtle.forward()
  end
  turtle.turnRight()
  turtle.up()
end


buildLayer(shrek)