I had 3 onsite interviews total, no phone screening. Process spanned 2-3 weeks.
1. I first spoke with Head of Design, which was a 30-min intro chat. Introduced myself and got to ask whatever questions I had. I was told that my portfolio will be reviewed again before they reach back out.
2. Got an email a few days later to join in for the whiteboard challenge. I got the same prompt as other folks here, but to address that - I doubt the team is expecting a specific answer from the interviewee. I was told the exercise is for the team to see how we worked. In hindsight, I believe it's more about our general attitude when collaborating, reception to different ideas, attachment or unattachment to different design processes, etc. (Frankly, I was personally all over the place and jumbled over my words 😂)
3. I was invited back about a week later for a 3.5 hour onsite, which involves a portfolio review and a few 1-v-1s. I definitely got to know the team more here (which was harder to do in the previous two on-sites). I was personally very happy to see the team embracing my weirder projects, which aren't necessarily 'design'. There was a slew of interesting open-ended questions as we chatted. The people I talked to were open and friendly, and I hold true to that statement now! :)
Having worked for a couple of weeks, I genuinely think there's a great team here. Everyone works collaboratively to achieve overall success, with ideas/designs shared openly with each other. Busy schedule. Actually nice people!