Step 1: The part list
Step 2: The kneading
Step 3: The molding
Step 4: The drying
pay attention it will not interfere with the internal shelf, as it almost happened to me ;-)
After some time (I waited some hours) you can remove the two toothbrushes and verify the joints work properly.
Now you've a very handy toothbrush holder, you don't need to become a professional tightrope walker to let the toothbrush remain clean, and you neither have to clean your bathroom cup every day!