Can't seem to get parts to weld together ?

Hi, everytime i generate a part with this script, it doesnt weld that piece to any other object.

The primary focus of this code is the elseif statement. That's where all the welding happens.

Thanks for the help.

local Tool = script.Parent
xSize = 3
ySize = 1
zSize = 5
Mouse = game.Players.LocalPlayer:GetMouse()
newBlock = nil
local Model = Instance.new("Model",workspace)

function createSingleInstance()
--  print(Mouse.Target)
--  print(type(Mouse.Target))
    if Mouse.Target.Name == "Baseplate" then

        local groundBlock = Instance.new("Part",workspace.Model)
        groundBlock.Name = "Block"
        groundBlock.Anchored = true
        groundBlock.Size = Vector3.new(xSize,ySize,zSize)
        groundBlock.Material = Enum.Material.Plastic
        groundBlock.Transparency = 1
        groundBlock.Position = Mouse.Hit.p

        groundBlock.BackSurface = Enum.SurfaceType.Smooth
        groundBlock.BottomSurface = Enum.SurfaceType.Smooth  
        groundBlock.FrontSurface = Enum.SurfaceType.Smooth    
        groundBlock.LeftSurface = Enum.SurfaceType.Smooth    
        groundBlock.RightSurface = Enum.SurfaceType.Smooth 
        groundBlock.TopSurface = Enum.SurfaceType.Smooth 

        groundBlock.Transparency = .9
        wait (.01)
        groundBlock.Transparency = .8
        wait (.01)
        groundBlock.Transparency = .7
        wait (.01)
        groundBlock.Transparency = .6
        wait (.01)
        groundBlock.Transparency = .5
        wait (.01)
        groundBlock.Transparency = .4
        wait (.01)
        groundBlock.Transparency = .3
        wait (.01)
        groundBlock.Transparency = .2
        wait (.01)
        groundBlock.Transparency = .1
        wait (.01)
        groundBlock.Transparency = 0

    elseif Mouse.Target.Name == "Block" then

        local newBlock = Instance.new("Part",workspace.Model)
        local target = Mouse.Target
        newBlock.Name = "Block"
        newBlock.Anchored = true
        newBlock.Size = Vector3.new(3,3,3)
        newBlock.Transparency = 1
        newBlock.Position = Mouse.Hit.p -- nearest surface?

        newBlock.BackSurface = Enum.SurfaceType.Weld  
        newBlock.BottomSurface = Enum.SurfaceType.Weld  
        newBlock.FrontSurface = Enum.SurfaceType.Weld  
        newBlock.LeftSurface = Enum.SurfaceType.Weld  
        newBlock.RightSurface = Enum.SurfaceType.Weld
        newBlock.TopSurface = Enum.SurfaceType.Weld

        --newBlock.CFrame = otherBlock.CFrame * CFrame.new(0, newBlock.Size.Y / 2 + otherBlock.Size.Y / 2, 0)


        workspace.Model:MakeJoints()
        newBlock.Anchored = false

        newBlock.Transparency = .9
        wait (.01)
        newBlock.Transparency = .8
        wait (.01)
        newBlock.Transparency = .7
        wait (.01)
        newBlock.Transparency = .6
        wait (.01)
        newBlock.Transparency = .5
        wait (.01)
        newBlock.Transparency = .4
        wait (.01)
        newBlock.Transparency = .3
        wait (.01)
        newBlock.Transparency = .2
        wait (.01)
        newBlock.Transparency = .1
        wait (.01)
        newBlock.Transparency = 0

    end


end

Tool.Activated:Connect(createSingleInstance)

What it looks like in game: https://imgur.com/a/6tYFihh