Using my very old tried and tested technique, I took some oranges out of the freezer, weighed them, put them in the pressure cooker whole with the water, and allowed them to thaw overnight. The next day I cooked them, leaving till the third day, when they were removed, cut very finely, the pulp and pips sieved. The remains are then cooked again to extract all the pectin with the remainder of the water. Finally the lemon juice and warmed sugar is added.
After ten minutes or so, the marmalade is ladled into the sterilised jars. Usually I try to design and get the jars stored away in a dark cupboard the following day.