A backside boardslide means approaching the box from the heelside, ollieing on, and rotating 90 degrees so the board is perpendicular to the feature. You slide across with the box between your bindings. This is the classic first board trick beyond a 50/50.
The ollie-and-rotate happen as a single motion. There's no "ollie first, then rotate" pause. As you pop off your tail, wind your shoulders 90 degrees so the board follows underneath you. When you land on the box, it should already be perpendicular to the feature. Attempting to rotate after you land is how you slip out and slam onto your back.
On the slide itself, your weight needs to be centered exactly over the box. Leaning slightly heelside catches the heel edge (and throws you onto your back); leaning toeside catches the toe edge (throwing you onto your face). Imagine a plumb line straight down from your belly button to the middle of the box. That's your target balance point. Ride off the end, then rotate the extra 90 degrees back to forward while in the air, landing on snow pointing down the feature again.
Watch more here:
Source: Snowboard Addiction · How To Backside Boardslide On A Snowboard
Key tips
- Approach with enough speed to clear the full box
- Ollie and rotate together. Don't try to rotate once you're on the box
- Keep your weight centered over the box
- Look at the end of the box to stay balanced
- Ride off the end and rotate back to forward
- Learn this on a flat low box before trying a down box or rail
- If you catch an edge, you usually leaned too far back. Keep the weight centered over the binding screws