Clean the leeks and cut them into round slices (the white part and a little of the tender green part), finely chop the onion and coarsely chop the fennel or dill.

Clean the leaf celery and the roots which you place into a bowl of water with the lemon juice and cut them into thick slices.

Wash the pork belly slices.

Boil the roots and the leaf celery for about 10 minutes then strain.

Place the wine, the leeks and the onion in a large pot until they absorb all the wine and then add the fennel with the allspice and mix.

Push the leeks to the middle of the pot and add the pork belly slices so that they cover the bottom of the pot and they are covered with the leeks, let them sauté well so that they let out their fat (the recipe doesn't have any oil). 

Add the celery plus boiled water until the food is covered, then season with salt.

When it starts to boil turn down the heat to half and let the food simmer.

When it is ready and the stock fills a little more than a cup, mix that stock with the lemon juice and the corn starch in a bowl, pour it over the food and let it boil vigorously for a couple of minutes to thicken.