How to generate navmesh for side scroller template level?

This is a simple repro.
If you just start a new project using the (3D) Side Scroller template in UE4 (NOT the 2D Side Scroller template!) and then add a NavMeshBoundsVolume which encompasses the entire level, it will not generate a navmesh that covers any of the surface the player actually runs around on except for the floor and the left most and right most high walls.
All the surface in between are devoid of a navmesh.

I have tried messing with all the generation settings on the RecastNavMesh to no avail.
I also tried making the bound volume only cover one of the static meshes that was in the air, and tried a single mesh that was touching the floor. Neither works.

So…how in the world can I generate a navmesh for multiple blocks like this?
Am I supposed to just do it all with NavLinks?

Closed, because of duplication: