Nouns ending in -ette are usually feminine.
The suffix often forms a diminutive.
Is assiette masculine or feminine?
l'assiette
The rule behind it
99.3% of -ette nouns are feminine
In context
J'ai lavé les assiettes après le souper.
I washed the dishes after supper.
Apportez-moi une assiette propre et emmenez la sale.
Bring me a clean plate and take the dirty one away.
Il n'y a pas d'assiettes propres.
There are no clean plates.