A backward slide is the forward slide turned the other way round. You ride up onto the box with the board across the feature at 90 degrees, but this time your back points at the end of the box and you slide facing the way you came. Same position, opposite direction - and it's the blind one.
It feels sketchy at first because you can't see where you're going while you slide. The fix is to trust the approach: set the angle up right, turn cleanly as you leave the ramp, land with a flat base, and the handle keeps you on line across the box. Twisting round to look over your shoulder mid-slide usually throws your weight off.
At the park you normally pop onto the box and rotate in the air rather than ride up and turn, and the position has two trick names depending on the edge you approach on: from heelside it's a back lip (HS BS90), from toeside it's a frontboard (TS BS90). Same rotation, same slide, different edge.
More tips here:
Source: Lagoon Watersports · How to Backside Lipslide on your Wakeboard
Key tips
- The turn goes the other way from the forward slide. You rotate your back toward the end of the box, which feels blinder than turning your chest to it
- Turn as you leave the ramp, not on the box surface
- Keep your weight centered once you're on the box
- Keep your head still and your eyes level. Twisting round to find the end of the box is what tips you over
- Ride off the end and turn back to normal riding
- The handle stays at your front hip through the slide. Don't let it drift behind you
- Under-rotating is safer than over-rotating. A 70-degree slide still holds, a 110-degree slide catches the edge