I’ve been advised to cut the stalk at about 3 feet above ground. Supposedly the sap in that 3 feet will help the plant stay healthier than if you cut it all the way to the ground. Eventually that dying stalk withers from top down. When it’s weak and mostly withered (months later), just knock it over and it’ll become part of the mulch pile at the base of your plant.
Banana sap causes permanent dark stains on everything it touches, so I suggest you prepare for the sacrifice by donning your traditional banana clothing and drawing your traditional banana cutlass (machete) from its scabbard. Say a chant thanking the stalk for giving its life and its fruit into the world, and perform the sacred decapitation, piling the cuttings onto the base as mulch.
This is the tradition as I’ve inherited it. If others in the community have better ways, please share.