Multi-sport support
Besides skiing and snowboarding, Slopes supports a bunch of other winter sports such as mono-skiing, snowbiking, splitboarding and more. If you hike or skin uphill, you can also set your activity type to backcountry which will add the uphill segments to Apple Health, including speed and elevation gain.
If you don't see your sport initially, tap on More Activities to find it. Then after you pick it once, like Apple's native Workout app, it'll move that sport to the top of the list.