How to define a Multilevel ATO BOM so that while progressing the Sales Order in "Create-Configurati

The requirement  is to  understand in detail how  to define  a multilevel ATO BOM so  that while  progressing a CTO Sales Order  by running the "Create-Configuration -eligible" workflow activity a child * item should get create for a Subassembly under the top level * item

The  Child Subassembly needs  to be sourced from a different  Manf Org