Heat olive oil in a large skillet over medium heat. Add the ground turkey and black pepper. Cook, crumbling, until browned, 4-5 minutes.
Add the onion and bell pepper and cook until slightly softened, about 3 minutes.
Add the garlic, carrots and zucchini and cook, stirring, for 1 minute. Remove pan from heat.
Place about ½ cup of the marinara sauce in the bottom of the slow cooker and spread into an even layer.
Lay a single layer of noodles in slow cooker, breaking them up as needed to make them fit. Top noodles with 1/3 of the turkey/veggie mixture, then ¼ of the remaining sauce, and then ¼ of the shredded cheese.
Repeat noodles-turkey/veggie-sauce-cheese layers two more times.
For the top layer, arrange a single layer of noodles and top with the remaining sauce and cheese.
Cover and cook on low setting for 3 hours. Turn off slow cooker and let lasagna rest, covered, for 30 minutes before serving.