Chop all the products finely and put them in a pan with a nonstick coating on the stove until all the water that the vegetables release evaporates.
Add the salt and oil and stir every now and then. Then blend them and put on the pan again to dry after blending. Once you get a thick dough-like mixture, remove the mixture from the stove and distribute it onto baking paper.
Shape it into a rectangular sheet about 1/2″ (1 cm) thick and freeze it for about 12 hours. Then cut it into cubes. To store, wrap each cube in baking paper separately and keep in the fridge.
The resulting mixture yields 9 broth cubes. You can also substitute any of the vegetables with others of your choice.