Stir together pasta sauce and basil leaves, plus ½ cup water. Taste and add salt, if needed. Set aside.
Mix together mozzarella, provolone, fontina, and parmesan cheeses. Remove ½ cup of the cheese mixture and refrigerate.
Combine the remaining cheese with the ricotta, egg, garlic, and 1 teaspoon salt.
Cover the bottom of your crock pot with 1 cup of the sauce.
Top sauce with 3 noodles, breaking them to fit, if necessary.
Spread ⅓ of the ricotta mixture over the noodles.
Cover ricotta with the ⅓ of the remaining sauce. Top sauce with 3 noodles, then another ⅓ of the ricotta. Repeat these layers one more time.
Pour remaining sauce over lasagna.
Cover and cook lasagna on medium for 3 ½ to 4 hours, or until noodles are tender. (See note about cooking times.)
Turn off heat, then top lasagna with reserved ½ cup cheese.
Recover lasagna, then let sit for 10 minutes.
Serve immediately, sprinkled with additional basil. Enjoy!
Notes
My crock pot is older and cooks at a lower temperature than many newer models. The first time you make this, I recommend checking the lasagna after an hour. You don't want it to cook so fast that the bottom burns before the noodles are cooked. If necessary, reduce the heat setting after an hour.