Clean the vegetables you choose for your stock. Cut into chunks and in a large pot, add just enough water to cover the vegetables and boil until soft. Allow to cool and blend until smooth and there are no large chunks. Spoon the blended stock into ice trays and freeze.
 
Shown here are mushrooms, celery, white onion and courgette. Any vegetables will work as long as you boil them until they are soft enough to blend. The added bonus to blending the vegetables is that the stock retains the fiber content. If you desire a 'fiber-free' stock, simply strain the boiled vegetables instead of blending them and freeze the liquid in ice trays.
 
Yield for the ingredients shown here was 4 full ice trays and a small 250ml container.