Personally I don't use a wireless pad, but I have a wireless charging cradle at work (the S20 supports 15W wireless charging so I upgraded to this beauty). It's really easy to line up, just set it down on the cradle base and the width lines up almost perfectly.

Edit: I didn't think about the fact that you'll have a cord sticking out the bottom of the phone. You can also charge the phone sideways but you have to place the phone centered on the cradle, a bit trickier than vertical.