Simple Play Den for kids

Just wondering if anyone has any suggestions as to how to go about making the wood frame for this play den. I would like it to be able to come apart for storage.

I was thinking of just painting a drop cloth like a house instead of the pricey throw.

Here's the link to what I'm talking about:

http://www.donnawilson.com/283-house-throw-play-den-set.html

Thanks for any insight.