How to make a noclip ablilty?

If you have FilteringEnabled, you could try this in a local script inside StarterGui, where you would have a part in workspace called Floor that the player could walk on (to prevent them from falling through the baseplate)

local debounce = true
game:GetService("UserInputService").InputBegan:Connect(function(key,bool)
	if key.KeyCode == Enum.KeyCode.Z and debounce == true and bool == false then
		debounce = false
		local changedParts = {}
		for _,v in pairs(workspace:GetDescendants()) do
			if v:IsA("BasePart") and v.Name ~= "Floor" and v.CanCollide == true then
				v.CanCollide = false
				table.insert(changedParts,1,v)
			end
		end
		wait(10)
		for _,v in pairs(changedParts) do
			v.CanCollide = true
		end
		wait(5)
		debounce = true
	end
end)

Other options could be to use collision filtering, but you would need remote events to do this.