During my limited gliding time there was a side slip final approach which ended in kicking off the drift & rolling level as you touched down.
This final approach would be with the a/c tracking in a straight line on runway heading with the nose pointed sideways & the opposite wing down, Shimples!
The slipping
turn was as implied, rudder & aileron reversed but balanced to produce a turn as well as lose height. Calling it a forward slip just confuses the issue. The thing is moving through the air in a straight line, where you draw that straight line through the airframe is anybodys. Also shimples. I can't see the problem