Usually, no. Nesting boxes should get elevated one to three feet above the ground, and chickens can typically flap their way up without any issues. If the opening of the nesting box is narrow or if it gets elevated more than the minimum three feet, a perch on the outside of the box is helpful.  Heavier breeds like Bantams could use ramps, but for the most part, all chickens can get to their boxes with a few flaps. The best bet is to keep an eye on your flock. If the hens have trouble accessing the nesting box - then add accommodation.