What you will need:
-A cheap plastic cup.
-Exacto knife or razorblade.
-Marker (non permanent)
Step 1: First Step: Acquire a Cup and Trace Outline on Paper
Next you need to trace the bottom of the cup along the corner of a sheet of paper so that the circle is tangent along two sides of the paper.
Step 2: Draw Guide Marks
The small x in each corner designates special points for my particular pattern. In this case I use a ninja star-looking patten.
Step 3: Draw Your Pattern Inside Your Circle
I cut square holes about half an inch long on each side. Then I tapered the entry holes so that the toothbrushes can be easily removed. You may try experimenting with different sizes for your toothbrush.
Step 4: Cut Your Template and Tape to Cup Bottom
After you cut out your template, it needs to be mounted or adhered temporarily to the bottom of your cup.
I used clear tape to keep my template in place. Don't forget to trace around your template once it's on your cup. You will use these trace lines to cut out the pattern.
Step 5: Use Exacto Knife or Other Sharp Blade to Cut the Pattern
This is the most difficult part mainly because it requires good cutting and trimming skills. Your craftsmanship with a knife will determine the outcome, but if it's not perfect don't worry...remember it's just a toothbrush holder anyway ;)
I used the straight edge sides of the cup as a guide for the legs. It turned out okay. Also be sure not to cut all the way down to the lip of the cup because you may lose some rigidity (which you may or may not want).
Hopefully this was useful or, at the very least, gave you some ideas about alternative ways to hold your toothbush.