Most hardware stores sell deep covers for protruding outlets. These feature extra wide bezels on the side of the cover. Most do not go over a few inches in depth. It is important to purchase the right size and shape for the outlet. Check the prong type, the depth, and the number of outlets on the cover before purchasing. It is also possible to make a custom cover using either PVC plastic or wall panelling.
Fit the cover over the protruding outlet and push it down. If possible, place the edges of the cover flat against the wall. If not, use a pencil to outline where the screws should go and find screws that make the full distance. Mark the holes on the wall and drill them and then fasten the wall socket to the wall.
If there is a gap between the wall and the outlet cover, fill the space with plaster such as patching plaster or silicone. Wait for the filler to dry and then paint over it so that it matches the wall or the socket. Snap the cover plate over the top of the outlet to finish the look.