If you want to say OF as in the sentence “A glass of water”.
Simply miss out the word OF
a cup of water.
eine Tasse Wasser
It is the plate of the dog / It is the dog’s plate
Es ist der Teller des Hundes.
In other words OF is DES and you add an S to the end of the noun.
It is the plate of the lobster.
Es ist der Teller des Hummers.
It is the plate of the aunt.
Es ist der Teller der Tante.
Without the S
The uncle’s relation is noisy.
Die Verwandte des Onkels ist laut.
nice
nett