I do not recommend using store-bought stock as you want the best quality stock with very little salt and the cleanest flavour possible. You can use my recipe to make a fantastic homemade Thai-style chicken stock, but in a pinch, you can just boil some chicken or pork bones for a couple of hours and add a bit of salt so it tastes like a very mildly flavoured soup. Do not make it salty as this broth will reduce as you eat. And it's a good idea to have more stock than you need as backup so you have enough to refill the pot if needed; you never know how much broth people are gonna take or how much will boil away.