I couldn't figure this out for the life of me, so I'm documenting it here.

When you want to add a subfolder, how do you do it?

Here is a folder off the root /schedule/

<location name="schedule" path="/schedule/" themeDir="schedule">
  <url name="schedule_default" path="schedule.aspx" pattern="schedule.aspx" physicalPath="##themeDir##" vanity="{2}" page="schedule.aspx" />
</location>

To make an entry for a subdirectory of /schedule, we need to make a separate entry. This entry is for /schedule/stunts/

<location name="schedulestunts" path="/schedule/stunts/" themeDir="schedule/stunts">
  <url name="schedule_stunt" path="ondemandfreepreview.aspx" pattern="ondemandfreepreview.aspx" vanity="{2}" physicalPath="##themeDir##" page="ondemandfreepreview.aspx" />
</location>

I don't know if this is the proper way to do this or not, but it got the job done. Please leave improvements if you have any!