Step 10:

We're reaching a critical mass here! I had to do the only logical thing after it started dripping down the side:
  
 
Step 11:

Cover again, and cook for another 15 minutes. Uncover, and season with some salt and pepper. I like kosher salt, but table salt is fine. Let simmer for about 5 minutes uncovered, until it's thickened up some. About this time, you should start boiling some water, and add your jumbo shells.

So now you have your shells in the water, and your marinara simmering to thick greatness.

Boil the shells according to the boxed direction, and drain. Throw them back in the pot to keep warm and flexible, and set aside while you make your stuffing.