Here are a few. We will add more as the Viaduct Closure looms and Bike Everywhere Month approaches.
West shoreline route, flat and scenic, from Alki Point.
White Center, as flat as it can be, with a hill between Puget Ridge and Pigeon Point down to the Spokane St Bridge.
Pioneer Square to Arbor Heights Direct [this is shortest route, but hilly, with a tough hill southbound from SW Alaska St up to Mt St Vincent]
If you have a fave, feel free to offer it up!