The oven has a captive cable for its mains power. I would prefer a socket for a standard IEC cable. This also made it easy to add a fuse and a power switch, by choosing a socket with these features built-in. I used the socket as a template for the cut-out in the metal back panel of the oven. I then drilled 2mm holes in each corner of the cutout and used a cutting disc in a rotary tool to make the cuts.

I tidied the sharp edges with a file. The socket is a tight fit into the hole and is secured by its locking tabs.