Hello fellow poler!
I have been stretching for flexibility for a while as I had none to start with. I'll give you my routine, although most of my stretching is for my legs as those are the worst.
I start with a Forward Fold for about 30 seconds.
I go into Swan/Hurdle Stretch and do 30 seconds each leg.
I do Downward Dog for about 30 seconds (try to get your heels on the floor)
I then do runners stretch, 30 seconds each leg.
Then I try Straddle stretch bringing my arms as far as I can in front of me for 30 seconds, I repeat this twice.
Then I do the same but bring my legs in front, and repeat that twice for 30 seconds.
Hip Opener stretch for 30 seconds each leg
I vary it now and again but this has brought my legs back from the brink of no flexibility. I am trying to work towards front splits as well.