How do you achieve ‘flow’?

What activities really help you get into a flow state? That state when you’re completely engrossed, nothing else matters, you’re focused on that thing alone. I’m newly diagnosed and have been struggling with workplace stress and anxiety, I’m looking for activities to engage me after work to reinforce and help me maintain that boundary between work and life. I find with the more ‘mindful’ activities my brain wanders back to the working day, replaying conversations, what I’ve done/not done etc. I need to find that thing that helps me block it out completely. What helps you achieve that ‘flow’ please?