Place the chicken thighs on a cutting board and season lightly with salt and pepper. In a large pot, heat the olive oil over medium heat until shimmering. Sear the chicken thighs for about 5 minutes per side until golden brown, then remove and set aside.
Add the diced carrots and celery to the same pot. Stir and cook for about 10 minutes until the vegetables soften slightly and release sweet aromas, with the vegetables turning tender but not browned.
Return the seared chicken thighs to the pot. Add the chicken broth, thyme sprigs, and bay leaves. Bring the mixture to a gentle simmer over medium heat.
Reduce the heat to low and cover the pot. Let the soup simmer gently for about 30 minutes until the chicken is cooked through and the flavors meld, with the broth developing a rich aroma.
Carefully remove the chicken thighs from the soup and place them on a cutting board. Shred the meat with two forks, discarding any bones if present.
Return the shredded chicken to the pot, stirring to combine. Squeeze the juice of the lemon into the soup, stirring well to brighten the flavors. Taste and adjust seasoning with salt and pepper.
Garnish with a little extra lemon juice or fresh herbs if desired. Serve the soup hot, with a slice of crusty bread if you like.
