I tried making a mini gingerbread house ornament a few years ago but I didn't like the way it looked. Since then I've come up with a better way to do it, which I'm going to share.
I started the same way, cutting all the sides of the house out of my card of choice; Amazon packaging. Then I glued all the bits together.
used here I was able to be more precise with the piping of the 'icing'.