I actually didn't unlock hard difficulty after being the hunter scenario like the other guide here. Not sure why, but oh well.
Instead, I found the easiest configuration to play a custom game on hard was to have a distance of 5 with 5 legendary places, no pets, 1 objective, and no to the card tracker. That put the game in hard mode.
At that point, it's just a grind to get through the five locations, as they will all be legendary and harder than usual to finish. I actually prefer to use the hunter as my avatar, as his hunting skill can nail pesky wolves and also nab that potential last food you are looking for. With only 5 locations, life can be an easily used resource. Once you travel for the 5th time, achievement unlocked.