How do you bake ambient occlusion?

I'm trying to bake AO into my scene, but I can't get it to work. Under the lightmapping settings I check the AO button but no matter what settings I use nothing happens when I generate lighting. Well, stuff happens, but there are no AO shadows rendered.
I can get AO to work if I add it as a filter to a camera, but I want to bake it and I don't think you can do that with a camera filter.
The scene has no lights and is lit by ambient light. The mesh is made with ProBuilder and I'm using U5.6.
What can I do to get this to work?

 

I thought so too, but it does nothing. I tried adding some basic cubes but they get no AO either.

 

Yea I still can't get the built in AO to work. Could use some pointers here.

 

I was about to post some settings but I managed to figure out why it didn't work. In addition to AO and other light settings you also had to set ambient mode to baked or nothing happens when you make a light map.

 

What does this mean? "ambient mode" of what?

 

Not 100% sure, but I think this is referring to the "Mode" dropdown on the Directional Lights in your scene. That, and making sure that the items in the scene had their "Static" toggle checked (next to the GameObject name in the inspector) is what finally got me results.