Peel and slice the aubergines and arrange in a colander, sprinkling each layer with salt.
Set aside for 2-3 hours so that the bitter juices drain away.
Place the aubergines in a pan and add the vinegar to cover the slices; poach for 5 minutes, then drain well.
Arrange the slices in a large glass jar, sprinkling the crushed garlic and oregano between the layers.
Fill the jar with oil and covet securely with a lid.
The pickle can be eaten after a week, but it keeps indefinitely.