How can I create a generic slot for an Alexa skill? So that I can create my own Todo app and it will recognise the free form text.
The Alexa blog announced a List Skill API. As mentioned above, the literal slot type is no longer supported for new skills.
If you create a custom slot with a number of values - depending on your expected response values with a single word or 2+ words - Alexa will catch also spoken words not on the list and pass them to your skill. Transcription of these words is best effort, and probably not perfect. Amazon discontinued the literal slot type because the results of speech-to-text were not good enough.
As you can sign up for a limited beta on the List Skill API, maybe this will solve your issue.