Greetings from the land of Israel: to make kanten recipes turn out more like "custard," it's important to use the amount of liquid and kanten that the recipe calls for in the recipe. After the flakes are added, bring to a boil and then simmer for 5 minutes as the recipe should say. Then, one extra step---use 1 tablespoon of Kuzu for each cup of liquid. Dilute the kuzu in a tablespoon of water and then add to the hot liquid --- The consistency at the end should be more custard like instead of "jello" like.
Good luck -- Annie