I gave Eliot's answer thumbs up because it sounds right to me. There's just one little correction in the second sentence. It's supposed to be: Die Küche ist das von mir am wenigsten geliebte Zimmer. So there's no plural-n at "geliebte". The plural would only occure if you'd want to say "The kitchen is one of my least favourite rooms" (implying that there are several rooms you don't like and the kitchen is just one of them). Then it would be: Die Küche ist eines der von mir am wenigsten geliebten Zimmer. The word Zimmer often leads to confusion because the plural and singular form are just the same (das Zimmer, die Zimmer).

....am wenigsten..... Das Zimmer, das ich am wenigsten mag, ist die Kueche. Die Kueche ist das von mir am wenigsten geliebten Zimmer. Die Kueche ist nicht gerade mein Lieblingszimmer. It's a bit tricky but you'll get the hang of it!