We have a patch panel with 16 XLR sockets on it installed in a wall. The
wall is coming out and so is the panel, which also happens to be a
junction for cables going to 2 other panels.

What is an appropriate and cost effective way of joining the cables and
should the joints be inside some sort of plastic box (it'll be under the
floor). Should provision be made for easy access to the joints in the
future.