Where else are you getting the "flow state" outside of climbing?

Multiple times...but not every time for sure. Poker. Poker tournaments to be my exact. Usually the larger field tournaments, deep somewhere on the 10th+ hour and in a multiday tournament. I experience flow state much like climbing, which I use to train and prep my mindset for those moments. 

Playing really loud doom metal

My job. I’m a cook. 

Writing
Writing code

Great topic!

I get the flow state sometimes doing terracing and trail/step-building for new routes. I tend to think of it more as "in the zone" - I can lose hours before I "come back".

It seems like a way to just shut off my mind and simply let the materials direct me. Sometimes it is almost magical the way things come together!

Skiing powder that's knee deep, mountain biking a flow trail like Fisher/Williams near Stanley, ID., building furniture with quality hardwood in my woodshop while listening to classic rock.

For me, a good game of chess or quarto. Mentally I'm focused on the next move, but also exploring multiple futures and outcomes. It's easy to get lost in that.   

Bathroom.

Briggs Lazalde wrote: Y'all tried drugs? 

My face melting off from 4-way windowpane is "flow state"? ;)

Kicking small dogs into space. That parabolic trajectory is balm.

B...a...l...m....

If you think the climbing flow state is nice, try meditation.  It's a different kind of flow state but much more present and vivid.  

For me Whitewater kayaking had me in that state way more than anything else.  In steep class V you really have no choice to think about anything other than your task at hand...in fact you can barely think its more like your body and brain doing the work for you.

Two other arctivities:  I'll second archery.  Target recurve shooting you have to be totally in tune with yourself (think able to release between breaths/heartbeats) especially at distance.  The second for me is sewing, especially on really detail oriented projects like button down shirts.

I do lots of adventurous sports, and definitely get flow state from climbing, skiing, mountain biking, whitewater kayaking, kiteboarding, etc... However, I also get flow state from my job, which I think is really cool. I work as an EMT on an ambulance, and am also a volunteer firefighter. When I get a good call for a car crash or some other critical patient, I get flow state from driving with lights and sirens and assessing/treating the patient. I have heard flow state described as happening when you are faced with a challenge that you are just able to meet and overcome. I am fairly new to emergency services, and I don't have a lot of experience, so often the challenge is formidable for me. I suppose that once I get so much experience that no call is much of a challenge the excitement might wear off, but for now it is very exciting. I think it is very comparable to extreme sports like climbing, because you have to make quick, confident decisions in situations where a wrong decision, instead of injuring yourself as in climbing, could injure your patient (which I think is even worse than injuring myself). Perhaps this is why many people who work in emergency services are also participants in extreme sports. The other really cool thing about my job is that in addition to getting the rush of adrenaline from the excitement of a critical incident, I also feel fulfillment from helping people and saving lives. I often have a hard time justifying taking risks in extreme sports just for my own pleasure, but as an EMT I get the same feeling from helping others.

I hope this helps your study! I think most people don't experience flow state from their work, so this might be a unique perspective.
Good luck!

Woodworking

Highlining for me, especially on lines that I am comfortable on, just bouncing and enjoying what i am experiencing at that very moment.

Playing drums in 6/8, especially anything by Opeth
Mountain biking
Easter Vigil church service
Edibles

Ayahuasca

Brazilian Jiu Jitsu and surfing. 

The "flow state" can happen in anything you do alot but its more of a repetitive motion endurance thing. Running is the classic "flow state" activity.

Don't confuse flow with concentration, you are probably just concentrating in Martial arts etc, its not a flow activity.