How to Write an Effective Software Design Document

A good, cathartic article. One of the best points is right at the top:

Writing a design doc forces you to think

Note that this is probably the most important part of writing a design. If you use an LLM to write the spec for you, you are skipping the important part: thinking.

Step 0: Write the design by hand. Please. Especially if you will be distributing it, but even if you're not going to. Being forced to think is so irreplaceable.