It's a lot easier than you would think.
Here is what I use
* 2 pounds lasagna sheets
* 2 cups hand cut 1/8-inch slices pepperoni
* 4 cups tomato sauce, recipe follows
* 1 pound ricotta
* 16 ounces shredded mozzarella Buy a block and shred yourself. Also get some fresh Motz that comes in a ball and is super soft for the very top of it.
* 2 pounds bulk Italian sausage, cooked
* 3/4 cup grated Parmesan
Directions
Preheat oven to 375 degrees F.
Boil 6 quarts of water, add pinch of salt, and cook pasta to almost done. Remove from water and shock in ice bath.
In medium saucepan add pepperoni and saute over medium heat until crispy. Remove from heat and drain on a paper towel.
In a 10-by-14-by-3-inch baking pan or dish, pour 1 cup of tomato sauce in bottom and around sides. Layer lasagna sheets on the bottom of the pan, overlapping by 1/2-inch. Add 1/3 amount of ricotta, 1/3 amount of mozzarella, 1/3 amount of sausage, then sprinkle generously with the Parmesan, add 1/2 cup tomato sauce, and 1/4 cup of pepperoni. Repeat this 2 more times.
On the very top sheet, top with remaining ricotta, tomato sauce, mozzarella, pepperoni, and dust with Parmesan. Bake for approximately 45 minutes. Remove from oven; let sit for 15 minutes. Cut and serve immediately