When is the proper time to conduct card sorting in the process of designing information architecture? Is it better to do this before attempting to do any design on the IA, or afterward (so as to validate it with users)? How does one analyze the findings?
There are 2 types of card sorting: Open and Closed. In simplified terms, open happens before IA, closed happens after.
Open: You are letting people organize items into groups and labeling them. The value of the exercise is talking to them and understanding their reasoning for doing so. How they think about the items, mental models.
Closed: You already have a good sense of the groups (from other research such as analytics, competitive, etc). People organize the items into the group labels you have already defined. You are evaluating how well your group labels perform.
More about this - https://www.nngroup.com/articles/card-sorting-definition/