Consider the requirements for writing a sequel to Animal Farm by George Orwell.
How would I be able to write a sequel to Animal Farm by George Orwell?
I've been pondering the idea of writing an actual sequel to Animal Farm.
Animal Farm is a fable and as such a sequel would be open to a broad interpretation. A sequel could focus on one of the characters - for example, Snowball - and his return to what is now called Manor Farm.
A sequel could focus on the life of the characters during their time on the farm - whilst the pigs gradually established their superiority and what really happened behind the scenes each time a commandment was changed.
Not matter how many good possibilities there are, you would have to obtain permission from the copyright holder before writing your sequel otherwise it would almost certainly be banned or not even accepted and published.
Animal Farm is such a highly recommended book on school curricula around the world that it is actually unlikely that any such permission would be forthcoming. You would have to have written several chapters for submission to the copyright holder so they can see your work but, even then, your style may not suit them and they would (will) most likely reject your request.
Persistence does sometimes see results but you would probably already have to be in the industry to get past the first hurdle. You would need an advisor who can help you correct your style to suit George Orwell's style to make this a worth sequel (in the copyright holder's eyes).