Place the chicken in a very large stockpot or divide by poaching the chickens in 2 pots. Add the peppercorns, garlic, bay leaves, carrots, celery, onions, lemon slices and herb bundle tied with string. Sprinkle with salt. Cover the chickens with water and bring to a boil. Reduce the heat to low, a rolling simmer. Simmer 1 hour 15 minutes to 1 hour 30 minutes, then cool the chickens in their stock. Strain the stock. Remove the skin and bones from the chickens and pull the meat into bite-size pieces.