This article from Nielsen Norman Group offers really practical advise for getting more effective UX design by putting ideation sessions very early in the process. It also is clear that group ideation is much more effective than doing that work individually.
This has absolutely been my experience as well, which is why I bring that practice with me wherever I work. I also love helping product teams develop a good ideation process by facilitating their collaborative design sessions.
Read the article here on nngroup.com