(This is not a paid-for/affiliate link post, I just had great difficulty tracking down a working solution for this so I thought I’d post the answer now I’ve found it!)
I tried a lot of things before finding the WorkOutDoors App. It lets you save a segment of a map (of any size) to your phone in complete zoomable detail and will even show a track of where you have been and a persistent compass pointing back to your start point. $2.99 on the App Store. Went from wanting to run in a straight line and back in unfamiliar places to feeling confident to go wherever after one run with it.
Some of the things I tried that didn’t work even remotely well enough: maps.me (app never appeared on phone), Sygic (one of many apps that wants you to plan a route on your phone and then download that and only that to the watch – didn’t even manage to achieve that), Yandex (seemed like it might work but only has Russian cities), ViewRanger, Apple Maps after scanning around the map a bit while online so it’s in memory (this was not totally useless but you can’t zoom).
this is old now, but entirely still relevant. it is incredible that an ideal solution has not yet been found. the apple watch is very capable of acting as a standalone device, especially for bicycling. do developers really not care about making a navigation app for the watch, or is there something behind the scenes that we are not aware of?
It’s crazy. WorkOutdoors is still the best I’ve found and does do the job but I can imagine much better!