Disassembling your office furniture is not needed because liquidators like to see the condition of the overall pieces being purchased and it ensures all dismantled pieces are kept in order.
Donating furniture and also depreciating the furniture / assets against what was originally paid can help with tax write offs. For legal purposes it is best to consult with an accountant.
The seller of the office furniture sends out a request for quotation from various liquidation companies. The seller usually has prepared details such as photos, quantities and timelines prior to reaching out to liquidators. Depending on the scenario of the liquidation the seller can expect to have the furniture sold from the premises via auction