Creating a custom input in Flutter is as simple as creating a normal widget, with the additional methods described earlier. We normally do this by extending the FormField<inputType> widget, where inputType is the value type of the input widget.

So, the typical process is as follows:

1. Create a custom widget that extends Stateful widget (to keep track of the value) and accepts input from the user by encapsulating another input widget, or by customizing the whole process, such as by using gestures.
2. Create a widget that extends FormField that basically displays the input widget created in the previous step and also exposes its fields.