What to say when a prospect asks for your portfolio (and you don't have one)

I don't have a traditional portfolio, but working in big tech taught me something about how companies land contracts.

It's all about making the client feel you're building something custom to their use case.

Same logic applies as a freelancer.

"Give me 48 hours and I'll put together a breakdown of exactly how I'd approach your problem."

Then do it. One page. Their situation, your thinking, the outcome you'd aim for.

A portfolio shows what you did for someone else. A breakdown shows what you'd do for them. Way more relevant.

Anyone else handled the portfolio question this way or found something else that works?