I think a reasonable paraphrase would be “[noun] who/which was [adjective,adjective,…]”

For example:

L’alien qui était grand, gros, moche, et vert…

Or even more compactly:

Le grand alien gros moche vert…

Either way, I’d put all or all but one of the adjectives after the noun (maybe you want to put one adjective which is the primary one – here, “big” – before the noun, but you could put them all after it).

However, it looks like native French speakers are also fine with doing things in a more “English” way and putting most of the adjectives before the noun (although leaving one after the noun which you’d never do in English), eg.:

Le grand, gros et moche extraterrestre vert…

You can also pile adjectives in french, before and after the noun.

I don’t think there’s any formal rule. This is mostly a question of style and usage (the section "Épithète liée" of this article explains this an interesting way). In certain specific cases, the position of the adjective changes the meaning (the article above includes a few words about that as well) but this is also a question of usage.

So we would say:

Le gros alien vert

Le gros alien vert et moche

Le gros, grand et affreux alien vert et malpoli

L’alien vert, grand, affreux, et malpoli

But we wouldn’t say (but in poetry, maybe):

Le gros, grand, affreux, malpoli et vert alien

Le bleu alien moche

Even if all of the sentences above are actually not incorrect.

And, specific case:

Un alien sale (an alien that is dirty)

doesn’t mean:

Un sale alien (a bloody alien, not to use an f-word)

Anyhow,

Le gros vert Alien
cloche
courait dans la plaine
moche.
La lune était pleine,
proche ;
pour lui quelle aubaine :
roches !
(Mais il se cassa tout de même la figure).