First put a screw in the basket, then put the basket on the pole. A shorter screw then in the pictures would be better, but I didn't have one at hand. I plan to cut and/or reshape those screws. The long screw with lots of exposed threads are a bit too sticky in the snow, but still ok for a casual skier.

I just stick them on the pole, and that was enough. Normally you would use a heat gun and hot glue to attach / remove the baskets.

This setup has been strong enough to handle skiing on tracks and frozen lakes for some hundreds of kilometers.