How do I slowly introduce off-leash hikes/exercise ?

[Snowshoe]

How old is Wrigley? My boy was off leash as soon as we got him and that's how I taught recall. If Wrigley is less than 16 weeks you might want to try it. You simply assign your word as he runs to you of his own accord when he gets fearful of being too far from you. Exactly the same as potty training, wait for the action, give your word while the action is in progress.

This chat from a UK dog board discusses it:

Puppy off lead

Some caveats: Must be just you and puppy and biggest one, the place must be safe. I have thousands of acres of bush and space where we were able to do this with no other dogs or people near and no roads. I realize not everyone lives in a rural area like I do.

[Wrigley'smama]

Wrigley just turned 15 weeks on Friday. Ya, I can't think of any real safe place to try it out. He'd either be in the street or bothering other park goers. I may be able to try sip early one morning at this park but it's still risky as it's not totally fenced.