You see a lot of footage from the backcountry nowadays where you can see people perform a slope cut (or a ski cut). It is a method to test the stability of a slope. The skier (or snowboarder) cuts the slope in an angle of 45 degrees with sufficient speed to see if the snowpack is stable. It is a method that is gaining popularity rapidly in Europe. Performed by experts and wannabees.
The idea of the slope cut is that if you trigger the avalanche, you do that under your own terms. The slope is cut on high speed at an angle of 45 degrees, and the slope cutter is aiming for a safe spot. This safe spot (or island of safety) could be some trees, a rock or a ridge just outside the path of the avalanche. If the slope cut is performed well you'll trigger an avalanche (or not) and the momentum of your speed and the direction will take out of the avalanche and to the safe spot.
The theory is great and correct if properly implemented, but what you don't see in all the movies is that you need a lot of knowledge to perform the slope cut.
Slope cuts are a great tool for snowpacks with a relatively soft and not too deep top layer. With the right pressure and technique this top layer might start sliding and your speed, direction and the safe spot keep you out of trouble. Especially since those soft slabs normally start sliding below you, but...
Slope cuts don't work on so-called hard or deep slabs. Slope cuts won't help to trigger weak layers deeper in the snowpack. Fortunately, these deeper layers are often difficult to trigger, but the extra weight that you put on the snow cover while slope cutting can be the trigger. And then the shit hits the fan. The avalanches are bigger, but more important, a so-called hard or deep slab will start sliding above you and not below you. Good luck staying out of the avalanche.
Is the slope cut a good tool? Yes, but you have to know how to perform it and you have to be prepares when the shit hits the fan. Slope cuts are no guarantee to prevent accidents.