For cooking our jumbo prawns recipes on the wok with yellow bell peppers we cut them so that they will be one of the first vegetable ingredients added to the wok. We want them still good and firm at the end, so we don't cut them too thin or small. If you want your bell peppers cut very thinly or into very small pieces, you should add them later in the course of cooking so they do not overcook.
Cut Yellow Bell Peppers ready for the Wokking