Hi,
While not making 12kW converters, and fwiw but so you have a comparison, when in UK in two different houses with carpeted floors, and a cat, and wearing man-made fibre static-producing jumpers, I had no ESD issues with any components or circuits made, and inevitably one or two things fell on floor. Everything was done sitting at a wooden table on top of a 2-inch thick block of wood about 25 x 25 inches square. Components stored in tupperware tubs of assorted shapes and sizes from takeaways, some in paper bags, some in anti-static bags they came in, some not and some parts with pins shorted together in bits of polystyrene, some not. An utterly unprofessional set-up, perils of the hobbyist..., but I had no damaged parts by doing this. CMOS ICs, delicate (imo) CMOS OAs, bjts, fets, regulators, ADCs, etc. Probably just lucky.
You could do a last/pre-presentation to client 'make sure all is well' test before packaging securely, maybe, to avoid unpleasant or embarrassing situations?