Start by rinsing the lentils under cold water until the water runs clear, then set aside.
Chop the carrots into small, even pieces for quick cooking, and dice the onion into a similar size for even flavor distribution.
If you have time, sauté the onion and carrots in a tablespoon of oil over medium heat until the onion is golden and fragrant, about 5 minutes. This step deepens their flavors and fills your kitchen with a warm aroma.
Add the rinsed lentils, sautéed vegetables (or raw if skipping sautéing), minced garlic, cumin, thyme, and vegetable broth into your slow cooker. Give everything a good stir to combine the flavors evenly.
Cover the slow cooker and set it to low for 6 to 8 hours, or high for 3 to 4 hours. During this time, the lentils will soften and absorb the spices, filling your home with a cozy, earthy scent.
Once cooking is complete, open the lid and stir the soup gently. The lentils should be tender and slightly broken down, with vegetables soft and fragrant. If the soup is thicker than you like, stir in a splash of broth or water.
Squeeze fresh lemon juice into the soup for brightness and stir well. Taste and adjust seasoning with salt or pepper if needed.
Ladle the hot soup into bowls, garnish with fresh herbs if desired, and enjoy the comforting, velvety texture and rich aroma of this simple lentil soup.
