1.In a large colander, combine the zucchini slices with 1/2 tsp of the salt. Let stand until the zucchini gives off its juices, about 30 minutes. Rinse well under cold running water to remove the salt, drain and pat dry with paper towels.
2.In a large skillet, heat the oil over medium heat. Add the onion and red bell pepper and cook, stirring often, until softened, about 5 minutes. Add the garlic and cook, stirring often, for 1 minute. Removed from the heat, add the zucchini, and mix well.
3.In a medium bowl, mix the bread crumbs, Parmesan cheese, Italian seasoning, the remaining 1/2 teaspoon salt, and the pepper.
4.Place half of the zucchini mixture in a buttered 3.5-qt slow cooker. Sprinkle with half of the crumb mixture. Top with the remaining zucchini mixture, the sprinkle with the remaining crumbs. Dot the top of the crumbs with melted butter.
5.Cover and slow cook until the zucchini is tender, about 4 to 5 hours on low.