How to create a site plan without using a template

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I have both HD Interior Designer 2018 and HD Architect 2020.  I need to create a site plan for my friends' living room so that I can help them with furniture arrangement.  However, from what I have found on the HD help section, that I can only pick one of HD's templates and modify it.  None of the templates come even close to the layout of the living room.  Is there no way to build a site plan from the beginning?

 

One more thing is that I did work with modifying one of the HD living room templates.  I made all the changes, saving as I went along.  At some point, I would lose the ceiling, roof, floor and foundation and couldn't get it back.  This has happened to me twice, and I have no idea what I did.

 

i really need some help with this, as I promised that I would get this project done soon.  Thanks.