1) Clue to answer first 2) Effortless beyond compare 3) Least arduous 4) Least brow-wrinkling 5) Least challenging 6) Least complex 7) Least complicated 8) Least demanding 9) Least difficult 10) Least hard 11) Least harsh 12) Least involved 13) Least likely to stump 14) Least onerous 15) Least puzzling 1) Simplest 
A trail requiring limited skill with little challenge to travel