order confirmation-back flushing

In one scenario x is final product.x1( semifinished),x2(spare) are dependent materials for final product. x1 has bom r1 and r2 (raw materials).I put all x1,x2,r1,r2 stock available in storage.

To get final product , only final assy of above materials by labour.PIR (md61) created for x and planning run.After planning run, planned order generated for x and converted in to production order and released.

My requirement is on confirmation of production order, backflushing of dependent materials as per bom should be done

what are the fields to be maintained for the above materials.

Is one work center (labour category) enough?

How routing is to be maintained for only assembling of final product.

please explain the entire scenario step by step