Parts Requirement Flow

Hi All,

I have one basic question on the parts requirement flow, based on the parts requirement from the Field Service, I believe Internal Sales Order is created , wanted to know that this process will directly create the Internal Sales Order or first Internal Requisition will be created and from that ISO will be created?

We have a requirement directly to create the ISO from one of the custom form i.e., we have all the details that are required to generate the ISO, if Parts requirement flow is generated ISO directly without the IR, then can we use the same packages which can be called from my custom form, can you please shred some light on this, also if possible can you share the API details .