Hi Andrea, 

Compound nouns don't normally have a preposition but a hyphen to link them together making them into a new noun -

Here are some examples of combinations of nouns, verbs, adverbs, adjectives, and past participles:

Un croque-monsieur

Un couvre-lit = A bedspread

Un perce-neige = A snowdrop

Un après-midi = An afternoon

Le savoir-faire 

Une belle-sœur = A sister in law

Un coffre-fort = A safe

Un passe-partout = A master key

etc.

Hope this helps!