Diagonal

local current = 1
turtle.select(current)
function check()
    while turtle.getItemCount()<3 do
        current = current + 1
        turtle.select(current)
    end
end

for i=1,32 do

    check()
    turtle.select(current)
    turtle.placeDown()
    turtle.forward()
    turtle.placeDown()
    turtle.turnLeft()
    turtle.forward()
    turtle.turnRight()
end