A dissertation is the longest piece you will write in your law degree, and the one where planning matters most. This is how I advise my students to approach it.
1. Choose a question, not a topic
"Autonomous weapons" is a topic. "Can existing humanitarian law regulate autonomous weapons?" is a question. A question gives you something to argue and a natural conclusion.
2. Plan your chapters around the argument
A typical structure is an introduction, the legal background, two or three analytical chapters and a conclusion. Each chapter should answer one sub-question that moves the argument forward.
3. Start the literature review early
It shows you what has already been said and where your contribution lies. See my guide on how to write a literature review.
4. Write as you research
Do not wait until you have "finished reading". Draft sections as you go; writing shows you what you still need to find.
5. Use your supervisor well
Bring specific questions and written drafts to meetings, and act on the feedback you get.
6. Leave time to edit
Aim to finish a full draft at least two weeks before the deadline. Use that time for structure, clarity, and checking every footnote and the bibliography.
I offer a full dissertation review with written comments and an hour of oral feedback. Ask about a review.