Disassembly: taking finished goods apart

Steps

Go to Operations → Production → Disassembly and click New disassembly.
Choose the finished good (any item with an active bill of materials) and the warehouse it is in - its BOM and stock are shown.
Enter the quantity to take apart - never more than is on hand (for a batch-tracked item, choose the batch, or first-to-expire goes first).
Full disassembly: every component comes back at the BOM quantities × the quantity (e.g. 2 bicycles → 2 frames, 4 wheels, 2 seats).
Partial disassembly: tick only the components you recover and give their quantities - up to what the BOM holds (e.g. 1 frame and 1 of the 2 wheels).
Choose the warehouse the components go into, and a batch number for batch-tracked components (else the disassembly number is used). Click Post disassembly.
In that one step the finished goods leave stock, the components come in, costed, and the journal is posted - no separate goods issue and goods receipt.

Serialised items are not on bills of materials, so serial numbers do not apply here; batches do.
Where an approval template for Disassembly applies (Settings › Approval setup), it waits for approval - nothing moves until it is approved - and posts when the last approver approves.