I always just make a text label that has a black background and set the position to Udim2.new(0,0,-0.05,0), and the size to Udim2.new(1,0,0.1,0). You can play around with the size and position until it is to your liking.
As @XdJackyboiiXd21 suggests, you can create a Frame of your choosing, set the size to something like UDim2.new(1, 0, 0.1, 0) (do not change the position because we want the UI to be on top, unless if you need to set a certain AnchorPoint to your frame), set your ScreenGui’s IgnoreGuiInset property to true, and playtest. Then you can adjust the UI to your liking.