Gather all ingredients, then set up your slow cooker on the counter.
Chop the carrots and celery into rough, bite-sized pieces, and set them aside on a plate.
Place the chicken thighs into the slow cooker, along with the chopped carrots and celery.
Add the minced garlic, grated ginger, and crushed lemongrass stalk to the slow cooker, distributing them evenly.
Pour in the chicken broth, then season generously with salt and pepper. If using, add soy sauce for extra umami.
Cover the slow cooker and cook on low for 6 to 8 hours, until the chicken is tender and falling apart, and the vegetables are soft.
Once cooking is complete, carefully remove the chicken thighs and lemongrass stalk from the slow cooker.
Shred the chicken with two forks until it’s nicely pulled apart, then return it to the broth.
Taste the broth and adjust seasoning with more salt, pepper, or soy sauce if desired.
Ladle the hot soup into bowls, garnishing with fresh cilantro or scallions for a burst of freshness.
Serve steaming, enjoy the fragrant, zesty flavors that make this soup a comforting yet invigorating meal.