I looked for a slope intercept foldable for the longest time that was simple and easy to use. Since I couldn't find one I decided to make my own. I looked at many different types of foldables and this is what I came up with. I have scanned my own notes I have used in my class so you can see how I used it and what it looks like.
There are 2 foldables per page which saves paper (YAY). All you need to do is print 2-sided and cut out the foldable and fold it over. Then cut on the dotted lines. Simple as that.