And how should the perfect fan look like?
The more lashes in fan you have, the bigger the opening of it should be, but less than 5mm between 2 side lashes (in case of 2D fan it should be less than 3mm). If fans are too opened, then the direction start ruining and lashes become messy, even if you do everything exactly as in lashmap.
No secret that an ideal fan must be symmetrical, so the distance between each extension should be absolutely equal, nevertheless how many lashes in fan you have. If you don't follow this rule, fans become crooked and can twist and bend over because of the uneven distribution of its mass.
3. The leg of a fan
Firstly, it should be thin. Secondly, the length of leg should be about 1/4 of lash' length (e.g. If a fan is 12mm, the leg of it should be about 3mm). If a leg is longer you can scoop too much glue with it, and the whole work will look less fluffy, but if its too small then fan become too wide and its difficult to attach it to the natural lash properly.