First you need to find out how large you want your folder to be. For this, I just found a normal folder and measured it, then drew a little sketch.
Now, duct tape! I imagine this would be a lot easier with a cutting board of some sort, but you could probably just use scissors too. Cut out strips about half an inch to an inch longer than your dimensions- because you will most likely need to trim parts of it.
Put your two pieces of duct tape back to back, then continue adding more, overlapping them.
Once you have both outside flaps of the folder complete, trim the edges so they are even with each other. You may want to make sure your folder will hold the right size of paper and add or trim as much tape as necessary. Tape the two outside parts together down the middle.
Next, you need to make the inside flaps of the folder! This is very similar to the outside. Overlap pieces of tape back to back, then tape them onto the inside of the folder.
Now for the design! You can really do whatever design you want, but I'm explaining the domo design that I did. For the mouth on the front, I cut out a 4 inch strip of red tape then cut out one inch triangles for teeth. This would probably be frustrating to do with scissors, I recommend an xacto knife.
For the eyes, I used a penny to cut around and make circles. Then I just cut a tiny bit of white for the eye glare.. thing.
For the inside I did the same as the front but with larger proportions. I believe it was 4x8? I used clear packing tape to put it over the flaps, but you could probably just make these the flaps too, I just thought it'd be easier to tape them on.
The last thing I did was use clear packing tape (again) over the design on the front to keep it from coming off, getting dirty, ect. You can just use scissors for that, it's much easier to cut!