Mapping a subdomain of an existing site domain to a new site

I’ve an external domain ankeetmaini.dev added as a custom domain for under-engineered.netlify.app.

Now I want to add a subdomain decks.ankeetmaini.dev to a new netlify site. I tried this by going to the uber level domain settings and added a CNAME pointing decks.ankeetmaini.dev -> ankeetdecks.netlify.app but on visiting decks.ankeetmaini.dev it shows 404

How do I fix it?

@ankeetmaini Welcome to the Netlify community.

Have you tried setting up a redirect to do this?

@gregraven I don’t see an option to do this. Only to add record.

@ankeetmaini It’s in the docs.

Redirects and rewrites | Netlify Docs -