This one can easily be made in less than an hour. For the assembly video below it took about 40 minutes, and I was taking my time to make sure and explain everything and get it right. So 30 minutes would be possible even for a first time build.
Here is a PDF of the Instructable that includes all the secondary images and annotations.
Here is a video explaining the assembly
It isn't really demonstrated much in action in that video, but it is pretty much the same as the original card in function.
Step 1: Tools and Supplies
Cardstock (the thicker the better, I use 0.012" thick and wouldn't suggest anything below that)
Stapler with staples
Small rubber band