Start in Elburg and cycle the Zuiderzee cycling route along several fringe lakes of the Flevopolder. On the other side, you'll see the new land, where you take an occasional peek. Elburg and Spakenburg lie on the old land and used to be coastal towns on the Zuiderzee before Flevoland existed.
Imagine yourself in a museum as you cycle through Elburg. Then cycle along Flevoland's peripheral lakes and enter Harderwijk. Cross the water with a bicycle foot ferry and you're at beach Horst. Explore Southern Flevoland, Zeewolde and cycle through the Horsterwold. This young forest is the largest continuous deciduous forest in the Netherlands. So hop on and discover it for yourself.
Note that this route goes from Elburg to Spakenburg, not back to Elburg. It's not a round trip.