The TouchScript examples lay out how it's reasonably frictionless to add Buttons to a Screen Space Overlay Canvas which are covered by the Hit Screen Space UI option in Standard Layer.
Simple Button taps as a use case don't seem to create any issues, but there is an annoying quirk with Sliders. On initial press, the value of the Slider always moves to 0 first, and then upon subsequent drag actions its value correctly snaps to wherever the user's finger is in screen space.

This happens even on the Screen Space Overlay Canvas demo with the four colored buttons, if you add a Slider to the same Canvas.

I noticed in the documentation there was an acknowledgement that GUI elements like Buttons "sort of" work and are more amenable to creating a Custom Layer. Is this an example of a situation where that's necessary? I've tried some hacky workarounds like disabling the interactable property of the slider and then re-enabling it on Drag, but I was hoping I wouldn't have to resort to a workaround.