Because of the high speeds required for full speed USB 3.0 communications, the USB C implementation needs very specific tolerances for it's cabling, with the high speed communication lines having shielded and very tight-twisted wire pairs. The higher current supply specification for powering devices also requires larger gauge wire than normal USB cables can provide, so USB 3.0 cables really need custom cabling solutions.
For most short distance situations, you could probably just use CAT6 cable, but it wouldn't provide enough conductors to pass all of the signals included in a USB C connector. A quick search also shows bulk cable available for USB 3.0 communications, but my initial result only shows cable with two high speed pairs and power in the cable. For very short lengths in a custom design, you may be able to use ribbon cable, routing the differential pairs next to each other, with a ground line on either side of each pair.
There are also ready-made extension cables and adapters available that are designed to be panel mounted.