The process took ~3weeks. There were 4 stages:
1) Phone interview: Quick, standard screening, lasted about 15minutes.
2) Open Culture Interview: I had mine via Skype because I was abroad at the time. It lasted for about an hour. After having read previous reviews, I was expecting to feel uncomfortable with the questions, but to me it felt just fine; I actually enjoyed the conversation, it didn't really feel like an interview to me. It was indeed more to check how you view yourself and how you react to uncomfortable stimuli, but nothing that made me uncomfortable at any point. It really is a good way to check if you would fit in the company's culture. Rule of thumb: if you didn't enjoy it, you will probably not enjoy working in GrantTree.
3) Role fit interview including:
i. Attention to detail test (quick & easy)
ii. Answer to a job-related email.
iii. Conversation with team members on how your skills, career aspirations & needs fit the role.
4) Shadow Day: Assuming that you reach this final stage, you are invited in a shadow day to see how the office is like and what are the interactions & dynamics of the team. I went for half a day, after they had just finished a welcome lunch for another new starter. After introductions & small talk, we went through the day-to-day tasks related to the role. Plenty of conversation, this didn't feel like an assessment either.
The recruiter was on top of my application and made sure I was informed about whether I had moved to the next stage as soon as they knew (i.e. shadow day on a Tuesday, I had an offer by Thursday).