1. Place the eggplant cubes in a colander, sprinkle with salt, and let it sit for about 20 minutes to draw out the bitterness. Rinse with water and pat dry with paper towels.
2. In the bottom of your slow cooker, spread out the onion and garlic. Layer the eggplant, zucchini, yellow squash, and bell pepper on top.
3. In a small bowl, combine the crushed tomatoes, tomato paste, basil, thyme, oregano, salt, and pepper. Stir to mix well.
4. Pour the tomato mixture over the layered vegetables in the slow cooker.
5. Drizzle the olive oil over the top of the vegetables.
6. Set the slow cooker to low and cook for about 6 hours, or until the vegetables are tender and the flavors have melded together wonderfully. You can also cook on high for about 3 to 4 hours if you’re in a pinch.
7. Give the ratatouille a gentle stir, being careful not to break the tender vegetables, and adjust the seasoning to your taste before serving.