I challenge anyone to enter the flow in a place that is not welcoming and noisy, not that it is impossible, but you have to be concentrate to be relaxed, and you are going to relax better if you are in a relaxed place. 

I usually enter the zone listening to jazz music and, once it happens, it is easy for me to get in and out comfortably. 

Another thing that can help you is a hot drink, no matter which one. A hot drink always keeps you company during the zone session. At least for me, it helps a lot.