As already established above, "layout" is a noun that defines the way that something looks or is arranged. As a noun, "layout" is always written as one word and should always be used with this meaning only.

Is layout one word or two?

Layout is a noun that means the way something is arranged. Lay out is a verb phrase that refers to the act of arranging something.

Is it layout or laid out?

Use lay out as a verb to describe positioning elements on a page. Use laid out as a verb in the past tense. Use layout to describe the result of laying out elements on a page.