What toolset is used to create IWatch custom faces

I watched the video listed at https://developer.apple.com/videos/play/wwdc2021/10003/ and found it very valuable. But what I don't know is:

  1. What IDE or toolset/libraries are required to build for watch?
  2. Once built, how do you get it on your watch?
What toolset is used to create IWatch custom faces
 
 
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