Layer diced carrots, celery, and onions in the bottom of a 6-Quart crockpot.
Place frozen chicken breasts on top of the vegetable layer.
Pour soup, water, bouillon, parsley, oregano, and pepper over the chicken and vegetables.
Place the lid on the crockpot and cook for 4 hours on the high setting or 7 hours on low.
After the cooking time has completed, remove the chicken from the crockpot and shred with two forks or cut into chunks. Return the meat to the crockpot.
Add frozen peas and stir to distribute evenly.
Remove the biscuits from their packaging. Flatten each biscuit, just a bit, with the palm of your hand or by rolling with a rolling pin. Cut each biscuit into four pieces and spread in a single layer over the top of the chicken mixture in the crockpot. If all of the biscuit pieces do not fit, discard the remaining pieces or use them for another purpose (I used 7 biscuits).
Continue cooking on HIGH for one additional hour. Do not open the crockpot lid as the steam and trapped heat are what cook the biscuits. The biscuits will be matte and puffy when done; if biscuits are still completely dough, cook them for a bit longer. (Try to assess doneness by looking through the lid rather than opening the crockpot.)