Starch allows you to reduce the cooking time of jelly at times. And the dessert is dense and solid.
Soak oatmeal in milk for 2-3 hours.
When the flakes are slightly swollen, put them on cheesecloth or a sieve, squeeze them out. Use the resulting milky-oatmeal liquid as the basis for jelly.
Put the mixture on medium heat. Add 1 tbsp. a spoonful of starch, previously slightly diluted in cold water. Salt to taste. Cook until boiling, stirring constantly, and then until the jelly thickens (about 1-3 minutes). After the jelly thickens, it is ready.