why is my block system making a diagonal shape instead of a square?

what im trying to do is create a block system which has 4 parts in each block and im trying to make it so it looks like this: what i want but for some reason its looking like this instead: weird shape into some diagonal shape instead of a square but I cant seem to find any bugs that are causing it in my code

local z, x = 0, 0
local z2, x2 = 0, 0
local size = Vector3.new(10,20,10)
local gap = 2.5
local blockamount = 2
--size of a block from :GetExtentsSize() = 22.5, 20, 22.5

local function createblock()
    local model = Instance.new("Model")
    local part = Instance.new("Part")

    for blockcolumn = 1,blockamount do
        for blockrow = 1,blockamount do
            local part = Instance.new("Part")

            part.Anchored = true
            part.Size = size
            part.CFrame = part.CFrame + Vector3.new(z+size.Z,size.Y/2,x)
            part.Parent = model

            z = z + size.Z + gap
        end

        z = 0
        x = x + size.X + gap
    end

    model.Name = "block"
    model.Parent = workspace
    part.Transparency = 1
    part.Anchored = true
    part.CFrame = CFrame.new(model:GetBoundingBox().Position)
    part.CanCollide = false
    part.Name = "root"
    part.Parent = model
    model.PrimaryPart = part

    return model
end

for column = 1,5 do
    local hold

    for row = 1,5 do
        local block = createblock()
        local size2 = block:GetExtentsSize()

        hold = size2
        block:SetPrimaryPartCFrame(block.PrimaryPart.CFrame + Vector3.new(z2+size2.Z,0,x2))
        z2 = z2 + size2.Z + gap
    end

    print(z2,x2, "column "..column)

    x = 0
    z = 0
    z2 = 0
    x2 = x2 + hold.X + gap
end

and the output of the code from the print statement is this - 125 0 column 1 - 125 25 column 2 - 125 50 column 3 - 125 75 column 4 - 125 100 column 5