Easiest, cheapest, fastest, toughest fly that catches fish
It doesn't get much easier than this. The body of the fly is nothing but a short length (length to suit your taste) of parachute chord. Para chord is available in many colors these days but OD green is one of my favorites. I've caught several species of fish on these flies in salt, brackish and fresh water.
I'm attaching 2 photos. One shows the completed fly and the second shows the little gizmo that keeps the tail from fouling. I call the little gizmo protruding out from the tail a "Snazzle." My Dad kept his flies from fouling this way. In this fly, the "snazzle" is made of 20# Steelon but I usually use 30-40# mono.
I purposely fouled the tail around the hook to show the snazzle.