Mix the flour with the salt and then drill a hole in the center and add the hot water. Then knead the dough for 8-10 minutes either in the mixer or by hand until the dough is almost smooth. Cover the bowl with a clean towel and let it rest for 15 minutes.
Then knead the dough for 2-3 minutes to have a very smooth dough. Cover again and allow the dough to rest in the refrigerator for at least 1 hour. If after 1 hour the dough is not relatively soft leave it to rest more.
When the dough becomes soft and smooth, divide it into 4 equal pieces. Start with one piece and return the rest back to the fridge. Roll the dough and make 10-gram dough balls. To be sure of size it is good to use weight them. Sprinkle with flour and make sure they do not stick together.
Then with the help of a rolling pin we roll out each ball to 10 cm diameter disc. At this point the filling should be ready because otherwise the dough will dry and then the edges will not stick together. Add about 1 tablespoon of filling to the center of the dough and then fold the wrapper over the filling and, using your fingers, pleat the edges to seal. Repeat with the remaining fillings and wrappers.